Transcriber’s Note
Due to limitations of this format, some typographical features are not
possible. Italic and bold text is represented in this text as _italic_
and =bold=. Finally, the few superscripted characters are given
in-line, e.g. 'Ltd' or 'A1'.
The colored plates and other illustrations cannot be given here.
The approximate positions of each, including any caption text, is shown
as [Illustration: caption]. Those which are shown in the middle of
paragraphs are positioned at the nearest paragraph break.
Please consult the detailed note at the end of this text for any
corrections made, and for any other observations about the text.
THE SEA SHORE
+--------------------------------------------------------------+
| THE OUT-DOOR WORLD SERIES. |
| |
| THE OUT-DOOR WORLD; or, the Young Collector's Handbook. |
| By W. S. FURNEAUX. With 18 Plates (16 of which are |
| Coloured), and 549 Illustrations in the Text. Crown |
| 8vo, 6s. 6d. net. |
| |
| FIELD AND WOODLAND PLANTS. |
| By W. S. FURNEAUX. With 8 Plates in Colour, and numerous |
| other Illustrations by PATTEN WILSON, and from |
| Photographs. Crown 8vo, 6s. 6d. net. |
| |
| BRITISH BUTTERFLIES AND MOTHS. |
| By W. S. FURNEAUX. With 12 Coloured Plates and 241 |
| Illustrations in the Text. Crown 8vo, 6s. 6d. net. |
| |
| LIFE IN PONDS AND STREAMS. |
| By W. S. FURNEAUX. With 8 Coloured Plates and 331 |
| Illustrations in the Text. Crown 8vo, 6s. 6d. net. |
| |
| THE SEA SHORE. By W. S. FURNEAUX. |
| With 8 Coloured Plates and over 300 Illustrations in the |
| Text. Crown 8vo, 6s. 6d. net. |
| |
| BRITISH BIRDS. By W. H. HUDSON. |
| With a Chapter on Structure and Classification by FRANK E. |
| BEDDARD, F.R.S. With 16 Plates (8 of which are Coloured), |
| and 103 Illustrations in the Text. Crown 8vo, 6s. 6d. net. |
| |
| LONGMANS, GREEN & CO., 39 Paternoster Row, London, E.C.4 |
| New York, Toronto, Bombay, Calcutta and Madras. |
+--------------------------------------------------------------+
[Illustration: Plate I, A ROCK-POOL]
THE SEA SHORE
BY
W. S. FURNEAUX
AUTHOR OF
‘THE OUTDOOR WORLD’ ‘BRITISH BUTTERFLIES AND MOTHS’
‘LIFE IN PONDS AND STREAMS’ ETC.
[Illustration]
_WITH EIGHT PLATES IN COLOUR_
_AND OVER THREE HUNDRED ILLUSTRATIONS IN THE TEXT_
_NEW IMPRESSION_
LONGMANS, GREEN AND CO.
39 PATERNOSTER ROW, LONDON, E.C.4
NEW YORK, TORONTO
BOMBAY, CALCUTTA AND MADRAS
1922
All rights reserved
+------------------------------------------------+
| BIBLIOGRAPHICAL NOTE. |
| |
| _First published in September, 1903._ |
| |
| _Re-issue at Cheaper Price, July, 1911._ |
| |
| _New Impression, November, 1922._ |
| |
| |
| _Made in Great Britain_ |
| |
+------------------------------------------------+
PREFACE
To sea-side naturalists it must be a matter of great surprise that of
the inhabitants of our coast towns and villages, and of the
pleasure-seekers that swarm on various parts of the coast during the
holiday season, so few take a real interest in the natural history of
the shore. The tide flows and ebbs and the restless waves incessantly
roll on the beach without arousing a thought as to the nature and cause
of their movements. The beach itself teems with peculiar forms of life
that are scarcely noticed except when they disturb the peace of the
resting visitor. The charming vegetation of the tranquil rock-pool
receives but a passing glance, and the little world of busy creatures
that people it are scarcely observed; while the wonderful forms of life
that inhabit the sheltered nooks of the rugged rocks between the
tide-marks are almost entirely unknown except to the comparatively few
students of Nature. So general is this apparent lack of interest in the
things of the shore that he who delights in the study of littoral life
and scenes but seldom meets with a kindred spirit while following his
pursuits, even though the crowded beach of a popular resort be situated
in the immediate neighbourhood of his hunting ground. The sea-side
cottager is too accustomed to the shore to suppose that he has anything
to learn concerning it, and this familiarity leads, if not to contempt,
most certainly to a disinclination to observe closely; and the visitor
from town often considers himself to be too much in need of his
hard-earned rest to undertake anything that may seem to require energy
of either mind or body.
Let both, however, cast aside any predisposition to look upon the
naturalist’s employment as arduous and toilsome, and make up their minds
to look enquiringly into the living world around them, and they will
soon find that they are led onward from the study of one object to
another, the employment becoming more and more fascinating as they
proceed.
Our aim in writing the following pages is to encourage the observation
of the nature and life of the sea shore; to give such assistance to the
beginner as will show him where the most interesting objects are to be
found, and how he should set to work to obtain them. Practical hints are
also furnished to enable the reader to successfully establish and
maintain a salt-water aquarium for the observation of marine life at
home, and to preserve various marine objects for the purpose of forming
a study-collection of the common objects of the shore.
To have given a detailed description of all such objects would have been
impossible in a work of this size, but a large number have been
described and figured, and the broad principles of the classification of
marine animals and plants have been given such prominence that, it is
hoped, even the younger readers will find but little difficulty in
determining the approximate positions, in the scale of life, of the
various living things that come within their reach.
Of the many illustrations, which must necessarily greatly assist the
reader in understanding the structure of the selected types and in the
identification of the different species, a large number have been
prepared especially for this work.
CONTENTS
CHAPTER PAGE
I. THE GENERAL CHARACTERISTICS OF THE SEA SHORE 1
II. THE SEA-SIDE NATURALIST 21
III. SEA ANGLING 34
IV. THE MARINE AQUARIUM 51
V. THE PRESERVATION OF MARINE OBJECTS 71
VI. EXAMINATION OF MARINE OBJECTS--DISSECTION 91
VII. THE PROTOZOA OF THE SEA SHORE 102
VIII. BRITISH SPONGES 115
IX. THE COELENTERATES--JELLY-FISHES, ANEMONES, AND
THEIR ALLIES 127
X. STARFISHES, SEA URCHINS, ETC. 157
XI. MARINE WORMS 172
XII. MARINE MOLLUSCS 190
XIII. MARINE ARTHROPODS 256
XIV. MARINE VERTEBRATES 306
XV. SEA WEEDS 343
XVI. THE FLOWERING PLANTS OF THE SEA-SIDE 391
INDEX 425
LIST OF COLOURED PLATES
_Drawn by_ MR. ROBERT LILLIE _and reproduced by_
MESSRS. ANDRÉ & SLEIGH, LTD., _Bushey_.
PLATE I--_A ROCK-POOL_ _Frontispiece_
PLATE II--_SEA ANEMONES_ _To face p. 142_
1, 2, 3. _Actinia mesembryanthemum._
4. _Caryophyllia Smithii._
5. _Tealia crassicornis._
6. _Sagartia bellis._
7. _Balanophyllia regia._
8. _Actinoloba dianthus._
PLATE III--_SEA ANEMONES_ _To face p. 150_
1. _Sagartia troglodytes._
2. ” _venusta._
3. _Actinia glauca._
4. ” _chiococca._
5. _Bunodes Ballii._
6. ” _gemmacea._
7. _Anthea cereus._
8. _Sagartia rosea._
PLATE IV--_ECHINODERMS_ _To face p. 168_
1. _Asterias rubens._
2. _Goniaster equestris._
3. _Ophiothrix fragilis._
4. _Echinocardium cordatum._
5. _Echinus miliaris._
6. ” _esculentus._
PLATE V--_MOLLUSCS_ _To face p. 222_
1. _Solen ensis._
2. _Trivia europæa._
3. _Trochus umbilicatus._
4. ” _magnus._
5. _Littorina littorea._
6. ” _rudis._
7. _Haminea_ (_Bulla_) _hydatis_.
8. _Tellina._
9. _Capulus_ (_Pileopsis_) _hungaricus_.
10. _Chrysodomus_ (_Fusus_) _antiquus_.
11. _Buccinum undatum._
12, 13. _Scalaria communis._
14. _Pecten opercularis._
15. " _varius._
16. " _maximus._
PLATE VI--_CRUSTACEA._ _To face p. 290_
1. _Gonoplax angulata._
2. _Xantho florida._
3. _Portunus puber._
4. _Polybius Henslowii._
5. _Porcellana platycheles._
PLATE VII--_SEAWEEDS_ _To face p. 354_
1. _Fucus nodosus._
2. _Nitophyllum laceratum._
3. _Codium tomentosum._
4. _Padina pavonia._
5. _Porphyra laciniata_ (_vulgaris_).
PLATE VIII--_SEAWEEDS_ _To face p. 384_
1. _Chorda filum._
2. _Fucus vesiculosus._
3. ” _canaliculatus._
4. _Delesseria (_Maugeria_) sanguinea_.
5. _Rhodymenia palmata._
6. _Chondrus crispus._
7. _Ulva lactuca._
OTHER ILLUSTRATIONS
FIG. PAGE
1. CHALK CLIFF 3
2. WHITECLIFF (CHALK), DORSET 4
3. PENLEE POINT, CORNWALL 5
4. BALANUS SHELLS 6
5. A CLUSTER OF MUSSELS 7
6. BREAKERS 8
7. ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF THE MOON 10
8. ILLUSTRATING THE TIDES 11
9. SPRING TIDES AT FULL MOON 12
10. SPRING TIDES AT NEW MOON 12
11. NEAP TIDES 13
12. CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE ON DIFFERENT
PARTS OF THE BRITISH COAST 16
13. THE VASCULUM 22
14. WIRE RING FOR NET 24
15. NET FRAME WITH CURVED POINT 24
16. RHOMBOIDAL FRAME FOR NET 24
17. RHOMBOIDAL NET 25
18. SEMICIRCULAR NET 25
19. THE DREDGE 25
20. THE CRAB-POT 26
21. AN OLD BIRD-CAGE USED AS A CRAB-POT 27
22. A YOUNG NATURALIST AT WORK 32
23. A GOOD HUNTING-GROUND ON THE CORNISH COAST 33
24. ROUND BEND HOOK WITH FLATTENED END 37
25. LIMERICK HOOK, EYED 37
26. METHOD OF ATTACHING SNOOD TO FLATTENED HOOK 38
27. METHOD OF ATTACHING SNOOD TO EYED HOOK 38
28. THE LUGWORM 39
29. THE RAGWORM 40
30. DIGGING FOR BAIT 41
31. METHOD OF OPENING A MUSSEL 42
32. FISHING FROM THE ROCKS 46
33. THE PATERNOSTER 48
34. SECTION OF AN AQUARIUM CONSTRUCTED WITH A MIXTURE OF
CEMENT AND SAND 54
35. CEMENT AQUARIUM WITH A GLASS PLATE IN FRONT 55
36. AQUARIUM OF WOOD WITH GLASS FRONT 56
37. HEXAGONAL AQUARIUM CONSTRUCTED OF ANGLE ZINC, WITH
GLASS SIDES 57
38. METHOD OF AERATING THE WATER OF AN AQUARIUM 65
39. AQUARIUM FITTED WITH APPARATUS FOR PERIODIC
OUTFLOW 67
40. JARS FOR PRESERVING ANATOMICAL AND BIOLOGICAL SPECIMENS 76
41. SHOWING THE DIFFERENT STAGES IN THE MAKING OF A SMALL
SPECIMEN TUBE 77
42. SMALL SPECIMEN TUBE MOUNTED ON A CARD 78
43. SMALL CRAB MOUNTED ON A CARD 82
44. SPRING FOR HOLDING TOGETHER SMALL BIVALVE SHELLS 84
45. THE TRIPLET MAGNIFIER 92
46. A SMALL DISSECTING TROUGH 93
47. CELL FOR SMALL LIVING OBJECTS 95
48. SHEET OF CORK ON THIN SHEET LEAD 99
49. WEIGHTED CORK FOR DISSECTING TROUGH 99
50. THE AMOEBA, HIGHLY MAGNIFIED 102
51. " " SHOWING CHANGES OF FORM 103
52. " " FEEDING 103
53. " " DIVIDING 104
54. A GROUP OF FORAMINIFERS, MAGNIFIED 105
55. A SPIRAL FORAMINIFER SHELL 106
56. A FORAMINIFER OUT OF ITS SHELL 106
57. THE SAME FORAMINIFER (FIG. 56) AS SEEN WHEN ALIVE 107
58. SECTION OF THE SHELL OF A COMPOUND FORAMINIFER 107
59. SECTION OF A NUMMULITE SHELL 108
60. _Globigerina bulloides_, AS SEEN WHEN ALIVE, MAGNIFIED 108
61. SECTION OF A PIECE OF NUMMULITIC LIMESTONE 109
62. A GROUP OF RADIOLARIAN SHELLS, MAGNIFIED 111
63. THREE INFUSORIANS, MAGNIFIED 113
64. A PHOSPHORESCENT MARINE INFUSORIAN (_Noctiluca_),
MAGNIFIED 114
65. SECTION OF A SIMPLE SPONGE 116
66. DIAGRAMMATIC SECTION OF A PORTION OF A COMPLEX SPONGE 117
67. HORNY NETWORK OF A SPONGE, MAGNIFIED 118
68. _Grantia compressa_ 120
69. SPICULES OF _Grantia_, MAGNIFIED 120
70. _Sycon ciliatum_ 121
71. _Leucosolenia botryoides_, WITH PORTION MAGNIFIED 121
72. _Chalina oculata_ 122
73. _Halichondria panicea_ 123
74. SPICULES OF _Halichondria_, MAGNIFIED 124
75. AN OYSTER SHELL, BORED BY _Cliona_ 124
76. SPICULES OF _Cliona_ 125
77. THREAD CELLS OF A COELENTERATE, MAGNIFIED 127
78. THE SQUIRREL'S-TAIL SEA FIR (_Sertularia argentea_),
WITH A PORTION ENLARGED 128
79. _Sertularia filicula_ 129
80. " _cupressina_ 130
81. THE HERRING-BONE POLYPE (_Halecium halecinum_) 131
82. _Tubularia indivisa_ 132
83. THE BOTTLE BRUSH (_Thuiaria thuja_) 132
84. _Antennularia antennia_ 133
85. _Aurelia aurita_ 135
86. THE EARLY STAGES OF _Aurelia_ 136
87. _Rhizostoma_ 136
88. _Chrysaora_ 136
89. _Cydippe pileus_ 137
90. SECTION OF AN ANEMONE 139
91. STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED 140
92. DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE 140
93. LARVA OF ANEMONE 140
94. THE TRUMPET ANEMONE (_Aiptasia Couchii_), CORNWALL;
DEEP WATER 144
95. _Peachia hastata,_ S. DEVON 145
96. _Sagartia pallida,_ DEVON AND CORNWALL 146
97. _Sagartia nivea,_ DEVON AND CORNWALL 147
98. _Corynactus viridis,_ DEVON AND CORNWALL 148
99. _Bunodes thallia,_ WEST COAST 150
100. _Bunodes gemmacea,_ WITH TENTACLES RETRACTED 151
101. _Caryophyllia cyathus_ 152
102. _Sagartia parasitica_ 153
103. THE CLOAK ANEMONE (_Adamsia palliata_) ON A WHELK
SHELL, WITH HERMIT CRAB 154
104. LARVA OF THE BRITTLE STARFISH 158
105. LARVA OF THE FEATHER STAR 160
106. THE ROSY FEATHER STAR 160
107. THE COMMON BRITTLE STAR 162
108. SECTION OF THE SPINE OF A SEA URCHIN 165
109. SEA URCHIN WITH SPINES REMOVED ON ONE SIDE 166
110. APEX OF SHELL OF SEA URCHIN 166
111. SHELL OF SEA URCHIN WITH TEETH PROTRUDING 167
112. INTERIOR OF SHELL OF SEA URCHIN 167
113. MASTICATORY APPARATUS OF SEA URCHIN 167
114. SEA URCHIN DISSECTED, SHOWING THE DIGESTIVE TUBE 168
115. THE SEA CUCUMBER 170
116. A TURBELLARIAN, MAGNIFIED 175
117. _Arenicola piscatorum_ 178
118. THE SEA MOUSE 179
119. TUBE-BUILDING WORMS: _Terebella, Serpula, Sabella_ 182
120. _Terebella_ REMOVED FROM ITS TUBE 183
121. A TUBE OF _Serpula_ ATTACHED TO A SHELL 185
122. _Serpula_ REMOVED FROM ITS TUBE 186
123. THE SEA MAT (_Flustra_) 187
124. _Flustra_ IN ITS CELL, MAGNIFIED 188
125. SEA SQUIRT 189
126. LARVÆ OF MOLLUSCS 191
127. SHELL OF THE PRICKLY COCKLE (_Cardium aculeatum_)
SHOWING UMBO AND HINGE; ALSO THE INTERIOR
SHOWING THE TEETH 192
128. INTERIOR OF BIVALVE SHELL, SHOWING MUSCULAR SCARS
AND PALLIAL LINE 193
129. DIAGRAM OF THE ANATOMY OF A LAMELLIBRANCH 194
130. _Mytilus edulis_, WITH BYSSUS 195
131. A BIVALVE SHELL (_Tapes virgineana_) 196
132. _Pholas dactylus_ 199
133. " " INTERIOR OF VALVE; AND _Pholadidea_
WITH ANIMAL 201
134. THE SHIP WORM 202
135. 1. _Teredo navalis._ 2. _Teredo norvegica_ 202
136. _Gastrochæna modiolina_ 203
137. 1. _Thracia phaseolina._ 2. _Thracia pubescens_,
SHOWING PALLIALLINE 204
138. 1. _Mya truncata._ 2. INTERIOR OF SHELL.
3. _Mya arenaria._4. _Corbula nucleus_ 205
139. _Solen siliqua_ 206
140. 1. _Solen ensis._ 2. _Cerati-solen legumen._
3. _Solecurtus candidus_ 207
141. _Tellinidæ_ 208
142. 1. _Lutraria elliptica._ 2. PART OF THE HINGE OF
_Lutraria_, SHOWING THE CARTILAGE PIT. 3. _Macra
stultorum._ 4. INTERIOR OF SAME SHOWING PALLIAL
LINE 210
143. _Veneridæ_ 211
144. _Cyprinidæ_ 213
145. _Galeomma Turtoni_ 214
146. 1. _Cardium pygmæum._ 2. _Cardium fasciatum._
3. _Cardium rusticum_ 215
147. _Cardium aculeatum_ 215
148. _Pectunculus glycimeris_, WITH PORTION OF VALVE
SHOWING TEETH, AND _Arca tetragona_ 216
149. _Mytilus edulis_ 217
150. 1. _Modiola modiolus._ 2. _Modiola tulipa._
3. _Crenella discors_ 218
151. _Dreissena polymorpha_ 219
152. _Avicula_, AND _Pinna pectinata_ 220
153. 1. _Anomia ephippium._ 2. _Pecten tigris._
3. _Pecten_, ANIMAL IN SHELL 222
154. _Terebratulina._ THE UPPER FIGURE REPRESENTS THE
INTERIOR OF THE DORSAL VALVE 224
155. UNDER SIDE OF THE SHELL OF _Natica catena_, SHOWING
THE UMBILICUS; AND OUTLINE OF THE SHELL, SHOWING THE
RIGHT-HANDED SPIRAL 225
156. SECTION OF THE SHELL OF THE WHELK, SHOWING THE
COLUMELLA 226
157. DIAGRAM OF THE ANATOMY OF THE WHELK, THE SHELL BEING
REMOVED 228
158. A PORTION OF THE LINGUAL RIBBON OF THE WHELK,
MAGNIFIED; AND A SINGLE ROW OF TEETH ON A MUCH
LARGER SCALE 229
159. EGG CASES OF THE WHELK 230
160. PTEROPODS 231
161. NUDIBRANCHS 234
162. " 235
163. SHELLS OF TECTIBRANCHS 236
164. CHITON SHELLS 238
165. SHELLS OF _Dentalium_ 238
166. _Patellidæ_ 239
167. _Calyptræa sinensis_ 241
168. _Fissurellidæ_ 241
169. _Haliotis_ 242
170. _Ianthina fragilis_ 242
171. _Trochus zizyphinus_. 2. UNDER SIDE OF SHELL.
3. _Trochus magnus._ 4. _Adeorbis subcarinatus_ 244
172. _Rissoa labiosa_ AND _Lacuna pallidula_ 244
173. SECTION OF SHELL OF _Turritella_ 245
174. _Turritella communis_ AND _Cæcum trachea_ 245
175. _Cerithium reticulatum_ AND _Aporrhais pes-pelicani_ 245
176. _Aporrhais pes-pelicani_, SHOWING BOTH SHELL AND ANIMAL 246
177. 1. _Odostomia plicata._ 2. _Eulima polita._
3. _Aclis supranitida_ 246
178. _Cypræa_ (_Trivia_) _europæa_ 247
179. 1. _Ovulum patulum_. 2. _Erato lævis_ 248
180. _Mangelia septangularis_ AND _Mangelia turricula_ 248
181. 1. _Purpura lapillus._ 2. EGG CASES OF _Purpura_.
3. _Nassa reticulata_ 249
182. _Murex erinaceus_ 249
183. OCTOPUS 251
184. _Loligo vulgaris_ AND ITS PEN 252
185. _Sepiola atlantica_ 252
186. _Sepia officinalis_ AND ITS 'BONE' 253
187. EGGS OF _Sepia_ 254
188. THE NERVE-CHAIN OF AN ARTHROPOD (LOBSTER) 257
189. SECTION THROUGH THE COMPOUND EYE OF AN ARTHROPOD 260
190. FOUR STAGES IN THE DEVELOPMENT OF THE COMMON SHORE
CRAB 261
191. THE BARNACLE 261
192. FOUR STAGES IN THE DEVELOPMENT OF THE ACORN BARNACLE 262
193. A CLUSTER OF ACORN SHELLS 263
194. SHELL OF ACORN BARNACLE (_Balanus_) 263
195. THE ACORN BARNACLE (_Balanus porcatus_) WITH APPENDAGES
PROTRUDED 264
196. A GROUP OF MARINE COPEPODS, MAGNIFIED 265
197. A GROUP OF OSTRACODE SHELLS 265
198. _Evadne_ 266
199. MARINE ISOPODS 267
200. MARINE AMPHIPODS 268
201. THE MANTIS SHRIMP (_Squilla Mantis_) 270
202. THE OPOSSUM SHRIMP (_Mysis chamæleon_) 271
203. PARTS OF LOBSTER'S SHELL, SEPARATED, AND VIEWED FROM
ABOVE 272
204. A SEGMENT OF THE ABDOMEN OF A LOBSTER 272
205. APPENDAGES OF A LOBSTER 273
206. LONGITUDINAL SECTION OF THE LOBSTER 274
207. THE SPINY LOBSTER (_Palinurus vulgaris_) 275
208. THE NORWAY LOBSTER (_Nephrops norvegicus_) 276
209. 1. THE MUD-BORER (_Gebia stellata_). 2. THE
MUD-BORROWER (_Callianassa subterranea_) 277
210. THE COMMON SHRIMP (_Crangon vulgaris_) 278
211. THE PRAWN (_Palæmon serratus_) 279
212. _Dromia vulgaris_ 282
213. THE HERMIT CRAB IN A WHELK SHELL 282
214. THE LONG-ARMED CRAB (_Corystes Cassivelaunus_) 287
215. SPIDER CRABS AT HOME 288
216. THE THORNBACK CRAB (_Maia Squinado_) 290
217. THE PEA CRAB (_Pinnotheres pisum_) 290
218. THE COMMON SHORE CRAB (_Carcinus mænas_) 291
219. THE SHORE SPIDER 294
220. THE LEG OF AN INSECT 295
221. TRACHEA OF AN INSECT, MAGNIFIED 296
222. SEA-SHORE INSECTS 298
223. MARINE BEETLES OF THE GENUS _Bembidium_ 302
224. MARINE BEETLES 303
225. TRANSVERSE SECTION THROUGH THE BONY FRAMEWORK OF A
TYPICAL VERTEBRATE ANIMAL 306
226. THE SEA LAMPREY 309
227. THE PILCHARD 310
228. THE SKELETON OF A FISH (PERCH) 315
229. THE INTERNAL ORGANS OF THE HERRING 316
230. THE EGG-CASE OF THE DOGFISH 319
231. THE SMOOTH HOUND 320
232. THE COMMON EEL 323
233. THE LESSER SAND EEL 326
234. THE THREE-BEARDED ROCKLING 327
235. THE SNAKE PIPE-FISH 328
236. THE RAINBOW WRASS (_Labrus julis_) 330
237. THE CORNISH SUCKER 330
238. THE FIFTEEN-SPINED STICKLEBACK AND NEST 331
239. THE SMOOTH BLENNY 333
240. THE BUTTERFISH 334
241. THE BLACK GOBY 335
242. THE FATHER LASHER 335
243. THE LESSER WEAVER 337
244. THE COMMON PORPOISE 341
245. _Callithamnion roseum_ 359
246. _Callithamnion tetricum_ 359
247. _Griffithsia corallina_ 361
248. _Halurus equisetifolius_ 361
249. _Pilota plumosa_ 361
250. _Ceramium diaphanum_ 363
251. _Plocamium_ 366
252. _Delesseria alata_ 368
253. _Delesseria hypoglossum_ 368
254. _Laurencia pinnatifida_ 371
255. _Laurencia obtusa_ 371
256. _Polysiphonia fastigiata_ 373
257. _Polysiphonia parasitica_ 374
258. _Polysiphonia Brodiæi_ 374
259. _Polysiphonia nigrescens_ 374
260. _Ectocarpus granulosus_ 378
261. _Ectocarpus siliculosus_ 378
262. _Ectocarpus Mertensii_ 378
263. _Sphacelaria cirrhosa_ 379
264. _Sphacelaria plumosa_ 379
265. _Sphacelaria radicans_ 380
266. _Cladostephus spongiosus_ 380
267. _Chordaria flagelliformis_ 380
268. _Laminaria bulbosa_ 384
269. _Laminaria saccharina_ 384
270. _Alaria esculenta_ 385
271. _Sporochnus pedunculatus_ 385
272. _Desmarestia ligulata_ 386
273. _Himanthalia lorea_ 387
274. _Cystoseira ericoides_ 388
275. TRANSVERSE SECTION OF THE STEM OF A MONOCOTYLEDON 391
276. LEAF OF A MONOCOTYLEDON 392
277. EXPANDED SPIKELET OF THE OAT 393
278. THE SEA LYME GRASS 395
279. _Knappia agrostidea_ 397
280. THE DOG'S-TOOTH GRASS 397
281. THE REED CANARY GRASS 397
282. MALE AND FEMALE FLOWERS OF _CAREX_, MAGNIFIED 399
283. THE SEA SEDGE 400
284. THE CURVED SEDGE 400
285. THE GREAT SEA RUSH 400
286. THE BROAD-LEAVED GRASS WRACK 401
287. THE SEA-SIDE ARROW GRASS 401
288. THE COMMON ASPARAGUS 401
289. THE SEA SPURGE 403
290. THE PURPLE SPURGE 404
291. THE SEA BUCKTHORN 404
292. _Chenopodium botryoides_ 405
293. THE FROSTED SEA ORACHE 406
294. THE PRICKLY SALT WORT 406
295. THE CREEPING GLASS WORT 407
296. THE SEA-SIDE PLANTAIN 408
297. THE SEA LAVENDER 408
298. THE DWARF CENTAURY 410
299. THE SEA SAMPHIRE 412
300. THE SEA-SIDE EVERLASTING PEA 413
301. THE SEA STORK'S-BILL 414
302. THE SEA CAMPION 416
303. THE SEA PEARL WORT 417
304. THE SHRUBBY MIGNONETTE 417
305. THE WILD CABBAGE 418
306. THE ISLE OF MAN CABBAGE 418
307. THE GREAT SEA STOCK 419
308. THE HOARY SHRUBBY STOCK 419
309. THE SCURVY GRASS 419
310. THE SEA RADISH 419
311. THE SEA ROCKET 420
312. THE SEA KALE 421
313. THE HORNED POPPY 422
THE SEA SHORE
CHAPTER I
_THE GENERAL CHARACTERISTICS OF THE SEA SHORE_
What are the attractions which so often entice us to the sea shore,
which give such charm to a ramble along the cliffs or the beach, and
which will so frequently constrain the most active wanderer to rest and
admire the scene before him? The chief of these attractions is
undoubtedly the incessant motion of the water and the constant change of
scene presented to his view. As we ramble along a beaten track at the
edge of the cliff, new and varied features of the coast are constantly
opening up before us. Each little headland passed reveals a sheltered
picturesque cove or a gentle bay with its line of yellow sands backed by
the cliffs and washed by the foaming waves; while now and again our path
slopes down to a peaceful valley with its cluster of pretty cottages,
and the rippling stream winding its way towards the sea. On the one hand
is the blue sea, full of life and motion as far as the eye can reach,
and on the other the cultivated fields or the wild and rugged downs.
The variety of these scenes is further increased by the frequent changes
in the character of the cliffs themselves. Where they are composed of
soft material we find the coast-line washed into gentle curves, and the
beach formed of a continuous stretch of fine sand; but where harder
rocks exist the scenery is wild and varied, and the beach usually strewn
with irregular masses of all sizes.
Then, when we approach the water’s edge, we find a delight in watching
the approaching waves as they roll over the sandy or pebbly beach, or
embrace an outlying rock, gently raising its olive covering of dangling
weeds.
Such attractions will allure the ordinary lover of Nature--the mere
seeker after the picturesque--but to the true naturalist there are many
others. The latter loves to read in the cliffs their past history, to
observe to what extent the general scenery of the coast is due to the
nature of the rocks, and to learn the action of the waves from the
character of the cliffs and beach, and from the changes which are known
to have taken place in the contour of the land in past years. He also
delights to study those plants and flowers which are peculiar to the
coast, and to observe how the influences of the sea have produced
interesting modifications in certain of our flowering plants, as may be
seen by comparing them with the same species from inland districts. The
sea birds, too, differing so much as they do from our other feathered
friends in structure and habit, provide a new field for study; while the
remarkably varied character of the forms of life met with on the beach
and in the shallow waters fringing the land is in itself sufficient to
supply the most active naturalist with material for prolonged and
constant work.
Let us first observe some of the general features of the coast itself,
and see how far we can account for the great diversity of character
presented to us, and for the continual changes and incessant motions
that add such a charm to the sea-side ramble.
Here we stand on the top of a cliff composed of a soft calcareous
rock--on the exposed edge of a bed of chalk that extends far inland. All
the country round is gently undulating, and devoid of any of the
features that make up a wild and romantic scene. The coast-line, too, is
wrought into a series of gentle bays, separated by inconspicuous
promontories where the rock, being slightly harder, has better withstood
the eroding action of the sea; or where a current, washing the
neighbouring shore, has been by some force deflected seaward. The cliff,
though not high, rises almost perpendicularly from the beach, and
presents to the sea a face which is but little broken, and which in
itself shows no strong evidence of the action of raging, tempestuous
seas; its chief diversity being its gradual rise and fall with each
successive undulation of the land. The same soft and gentle nature
characterises the beach below. Beyond a few small blocks of
freshly-loosened chalk, with here and there a liberated nodule of flint,
we find nothing but a continuous, fine, siliceous sand, the surface of
which is but seldom broken by the protrusion of masses from below. Such
cliffs and beaches do not in themselves suggest any violent action on
the part of the sea, and yet it is here that the ocean is enabled to
make its destructive efforts with the greatest effect. The soft rock is
gradually but surely reduced, partly by the mechanical action of the
waves and partly by the chemical action of the sea-water. The rock
being almost uniformly soft, it is uniformly worn away, thus presenting
a comparatively unbroken face. Its material is gradually dissolved in
the sea; and the calcareous matter being thus removed, we have a beach
composed of the remains of the flints which have been pulverised by the
action of the waves. Thus slowly but surely the sea gains upon the land.
Thus it is that many a famous landmark, once hundreds of yards from the
coast, now stands so near the edge of the cliff as to be threatened by
every storm; or some ancient castle, once miles from the shore, lies
entirely buried by the encroaching sea.
[Illustration: FIG. 1.--CHALK CLIFF]
The coast we have described is most certainly not the one with the
fullest attractions for the naturalist, for the cliffs lack those nooks
that provide so much shelter for bird and beast, and the rugged coves
and rock pools in which we find such a wonderful variety of marine life
are nowhere to be seen. But, although it represents a _typical_ shore
for a chalky district, yet we may find others of a very different nature
even where the same rock exists. Thus, at Flamborough in Yorkshire, and
St. Alban’s Head in Dorset, we find the hardened, exposed edge of the
chalk formation terminating in bold and majestic promontories, while
the inner edge surrounding the Weald gives rise to the famous cliffs of
Dover and the dizzy heights of Beachy Head. The hard chalk of the Isle
of Wight, too, which has so well withstood the repeated attacks of the
Atlantic waves, presents a bold barrier to the sea on the south and east
coasts, and terminates in the west with the majestic stacks of the
Needles.
[Illustration: FIG. 2.--WHITECLIFF (CHALK), DORSET]
Where this harder chalk exists the coast is rugged and irregular. Sea
birds find a home in the sheltered ledges and in the protected nooks of
its serrated edge; and the countless wave-resisting blocks of weathered
chalk that have been hurled from the heights above, together with the
many remnants of former cliffs that have at last succumbed to the
attacks of the boisterous sea, all form abundant shelter for a variety
of marine plants and animals.
[Illustration: FIG. 3.--PENLEE POINT, CORNWALL]
But it is in the west and south-west of our island that we find both
the most furious waves and the rocks that are best able to resist their
attacks. Here we are exposed to the full force of the frontal attacks of
the Atlantic, and it is here that the dashing breakers seek out the
weaker portions of the upturned and contorted strata, eating out deep
inlets, and often loosening enormous blocks of the hardest material,
hurling them on the rugged beach, where they are eventually to be
reduced to small fragments by the continual clashing and grinding action
of the smaller masses as they are thrown up by the angry sea. Here it is
that we find the most rugged and precipitous cliffs, bordering a more or
less wild and desolate country, now broken by a deep and narrow chasm
where the resonant roar of the sea ascends to the dizzy heights above,
and anon stretching seaward into a rocky headland, whose former
greatness is marked by a continuation of fantastic outliers and smaller
wave-worn masses of the harder strata. Here, too, we find that the
unyielding rocks give a permanent attachment to the red and olive weeds
which clothe them, and which provide a home for so many inhabitants of
our shallow waters. It is here, also, that we see those picturesque rock
pools of all sizes, formed by the removal of the softer material of the
rocks, and converted into so many miniature seas by the receding of the
tide.
[Illustration: FIG. 4.--BALANUS SHELLS]
A more lovely sight than the typical rock pool of the West coast one can
hardly imagine. Around lies the rugged but sea-worn rock, partly hidden
by dense patches of the conical shells of the _Balanus_, with here and
there a snug cluster of young mussels held together by their
intertwining silken byssi. The surface is further relieved by the
clinging limpet, the beautifully banded shells of the variable
dog-periwinkle, the pretty top shells, and a variety of other common but
interesting molluscs. Clusters of the common bladdery weeds are also
suspended from the dry rock, and hang gracefully into the still water
below, where the mantled cowry may be seen slowly gliding over the olive
fronds. Submerged in the peaceful pool are beautiful tufts of white and
pink corallines, among which a number of small and slender starfishes
may climb unnoticed by the casual observer; while the scene is
brightened by the numerous patches of slender green and red algæ, the
thread-like fronds of which are occasionally disturbed as the lively
little blenny darts among them to evade the intruder’s glance. Dotted
here and there are the beautiful anemones--the variously-hued animal
flowers of the sea, with expanded tentacles gently and gracefully
swaying, ready to grasp and paralyse any small living being that may
wander within their reach. Here, under a projecting ledge of the rock,
partly hidden by pale green threads, are the glaring eyes of the
voracious bullhead, eager to pounce on almost any moving object; while
above it the five-fingered starfish slowly climbs among the dangling
weeds by means of its innumerable suckers. In yonder shady corner, where
the overhanging rock cuts off all direct rays of the sun from the deeper
water of the pool, are the pink and yellow incrustations of little
sponges, some of the latter colour resembling a group of miniature
inverted volcanic cones, while on the sandy floor of the pool itself may
be seen the transparent phantom-like prawn, with its rapidly moving
spinnerets and gently-waving antennæ, suddenly darting backward when
disturbed by the incautious approach of the observer; and the spotted
sand-crab, entirely buried with the exception of its upper surface, and
so closely imitating its surroundings as to be quite invisible except on
the closest inspection. Finally, the scene is greatly enlivened by the
active movements of the hermit-crab, that appropriates to its own use
the shell which once covered the body of a mollusc, and by the erratic
excursions of its cousin crabs as they climb over the weedy banks of the
pool in search of food.
[Illustration: FIG. 5.--A CLUSTER OF MUSSELS]
Thus we may find much to admire and study on the sea shore at all times,
but there are attractions of quite another nature that call for notice
on a stormy day, especially on the wilder and more desolate western
coasts. At such times we delight to watch the distant waves as they
approach the shore, to see how they become gradually converted into the
foaming breakers that dash against the standing rocks and wash the
rattling pebbles high on the beach. The powerful effects of the sea in
wearing away the cliffs are now apparent, and we can well understand
that even the most obdurate of rocks must sooner or later break away
beneath its mighty waves.
[Illustration: FIG. 6.--BREAKERS]
The extreme mobility of the sea is displayed not only by the storm
waves, and by the soft ripples of the calm day, but is seen in the
gentle currents that almost imperceptibly wash our shores, and more
manifestly in the perpetual motions of the tides.
This last-named phenomenon is one of extreme interest to the sea-side
rambler, and also one of such great importance to the naturalist that we
cannot do better than spend a few moments in trying to understand how
the swaying of the waters of the ocean is brought about, and to see what
determines the period and intensity of its pulsations, as well as some
of the variations in the daily motions which are to be observed on our
own shores.
In doing this we shall, of course, not enter fully into the technical
theories of the tides, for which the reader should refer to
authoritative works on the subject, but merely endeavour to briefly
explain the observed oscillations of the sea and the general laws which
govern them.
The most casual observer must have noticed the close connection between
the movements of the ocean and the position of the moon, while those who
have given closer attention to the subject will have seen that the
relative heights of the tides vary regularly with the relative positions
of the sun, moon, and earth.
In the first place, then, we notice that the time of high tide in any
given place is always the same at the same period of the cycle of the
moon; that is, it is always the same at the time of new moon, full moon,
&c. Hence it becomes evident that the moon is the prime mover in the
formation of tides. Now, it is a fact that the sun, though about
ninety-three millions of miles from the earth, has a much greater
attractive influence on the earth and its oceans than the moon has,
although the distance of the latter is only about a quarter of a million
miles: but this is due to the vastly superior mass of the sun, which is
about twenty-six million times the mass of the moon. How is it, then,
that we find the tides apparently regulated by the moon rather than by
the sun?
The reason is that the tide-producing influence is due not to the actual
attractive force exerted on the earth as a whole, but to the difference
between the attraction for one side of the globe and that for the
opposite side. Now, it will be seen that the diameter of the
earth--about eight thousand miles--is an appreciable fraction of the
moon’s distance, and thus the attractive influence of the moon for the
side of the earth nearest to it will be appreciably greater than that
for the opposite side; while in the case of the sun, the earth’s
diameter is such a small fraction of the distance from the sun that the
_difference_ in the attractive force for the two opposite sides of the
earth is comparatively small.
Omitting, then, for the present the minor tide-producing influence of
the sun, let us see how the incessant rising and falling of the water of
the ocean are brought about; and, to simplify our explanation, we will
imagine the earth to be a globe entirely covered with water of uniform
depth.
The moon attracts the water on the side nearest to it with a greater
force than that exerted on the earth itself; hence the water is caused
to bulge out slightly on that side. Again, since the attractive force of
the moon for the earth as a whole is greater than that for the water on
the opposite side, the earth is pulled away, as it were, from the water
on that side, causing it to bulge out there also. Hence high tides are
produced on two opposite sides of the earth at the same time, while the
level of the water is correspondingly reduced at two other parts at
right angles with these sides.
This being the case, how are we to account for the observed changes in
the level of the sea that occur every day on our shores?
Let us first see the exact nature of these changes:--At a certain time
we find the water high on the beach; and, soon after reaching its
highest limit, a gradual descent takes place, generally extending over a
period of a little more than six hours. This is then followed by another
rise, occupying about the same time, and the oscillations are repeated
indefinitely with remarkable regularity as to time.
[Illustration: FIG. 7.--ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF
THE MOON]
Now, from what has been previously said with regard to the tidal
influence of the moon, we see that the tide must necessarily be high
under the moon, as well as on the side of the earth directly opposite
this body, and that the high tides must follow the moon in its regular
motion. But we must not forget that the earth itself is continually
turning on its axis, making a complete rotation in about twenty-four
hours; while the moon, which revolves round the earth in about
twenty-eight days, describes only a small portion of its orbit in the
same time; thus, while the tidal wave slowly follows the moon as it
travels in its orbit, the earth slips round, as it were, under the tidal
wave, causing four changes of tide in approximately the period of one
rotation. Suppose, for example, the earth to be performing its daily
rotation in the direction indicated by the arrow (fig. 8), and the tide
high at the place marked A¹, just under the moon, then, in about six
hours, this place will have been carried round to A², where the tide is
low; and, after similar intervals, to A³ and A⁴ successively, where
the tide is high and low respectively. Hence the daily changes are to a
great extent determined by the rotation of the earth.
But we have already observed that each change of tide occupies a little
more than six hours, the average time being nearly six hours and a
quarter, and so we find that the high and low tides occur nearly an hour
later every day. This is due to the fact that, owing to the revolution
of the moon round the earth in the same direction as that of the
rotation of the earth itself, the day as measured by the moon is nearly
an hour longer than the average solar day as given by the clock.
[Illustration: FIG. 8.--ILLUSTRATING THE TIDES]
There is yet another point worth noting with regard to the relation
between the moon and the tidal movements of the water, which is that the
high tides are never exactly under the moon, but always occur some time
after the moon has passed the meridian. This is due to the inertia of
the ocean, and to the resistance offered by the land to its movements.
Now, in addition to these diurnal changes of the tide, there are others,
extending over longer periods, and which must be more or less familiar
to everyone who has spent some time on the coast. On a certain day, for
instance, we observe that the high tide flows very far up the beach, and
that this is followed, a few hours later, by an unusually low ebb,
exposing rocks or sand-banks that are not frequently visible. Careful
observations of the motions of the water for some days after will show
that this great difference between the levels of high and low-water
gradually decreases until, about a week later, it is considerably
reduced, the high tide not flowing so far inland and the low-water mark
not extending so far seaward. Then, from this time, the difference
increases again, till, after about two weeks from the commencement of
our observations, we find it at the maximum again.
[Illustration: FIG. 9.--SPRING TIDES AT FULL MOON]
Here again we find that the changes exactly coincide with changes in the
position of the moon with regard to the sun and the earth. Thus, the
_spring tides_--those which rise very high and fall very low--always
occur when the moon is full or new; while the less vigorous _neap tides_
occur when the moon is in her quarters and presents only one-half of her
illuminated disc to the earth. And, as the moon passes through a
complete cycle of changes from _new_ to _first-quarter_, _full_,
_last-quarter_, and then to _new_ again in about twenty-nine days, so
the tides run through four changes from spring to neap, spring, neap,
and then to spring again in the same period.
[Illustration: FIG. 10.--SPRING TIDES AT NEW MOON]
The reason for this is not far to seek, for we have already seen that
both sun and moon exert a tide-producing influence on the earth, though
that of the moon is considerably greater than that of the sun; hence, if
the sun, earth, and moon are in a straight line, as they are when the
moon is full, at which time she and the sun are on opposite sides of the
earth, and also when new, at which time she is between the earth and
sun, the sun’s tide is added to the moon’s tide, thus producing the
well-marked spring tides; while, when the moon is in her quarters,
occupying a position at right angles from the sun as viewed from the
earth, the two bodies tend to produce high tides on different parts of
the earth at the same time, and thus we have the moon’s greater tides
reduced by the amount of the lesser tides of the sun, with the result
that the difference between high and low tides is much lessened.
[Illustration: FIG. 11.--NEAP TIDES]
Again, the difference between high and low water marks is not always
exactly the same for the same kind of tide--the spring tide for a
certain period, for example, not having the same limits as the same tide
of another time. This is due to the fact that the moon revolves round
the sun in an elliptical orbit, while the earth, at the same time,
revolves round the sun in a similar path, so that the distances of both
moon and sun from the earth vary at different times. And, since the
tide-producing influences of both these bodies must increase as their
distance from the earth diminishes, it follows that there must be
occasional appreciable variations in the vigour of the tidal movements
of the ocean.
As the earth rotates on its axis, while at the same time the tidal wave
must necessarily keep its position under the moon, this wave appears to
sweep round the earth with considerable velocity. The differences in the
level of the ocean thus produced would hardly be appreciable if the
earth were entirely covered with water; but, owing to the very irregular
distribution of the land, the movements of the tidal wave become
exceedingly complex; and, when it breaks an entrance into a gradually
narrowing channel, the water is compressed laterally, and
correspondingly increased in height. It is thus that we find a much
greater difference between the levels of high and low tides in
continental seas than are to be observed on the shores of oceanic
islands.
We have occupied so much of our time and space in explanation of the
movements of the tides not only because we think it desirable that all
who delight in sea-side rambles should understand something of the
varied motions which help to give such a charm to the sea, but also
because, as we shall observe later, these motions are a matter of great
importance to those who are interested in the observation and study of
marine life. And, seeing that we are writing more particularly for the
young naturalists of our own island, we must devote a little space to
the study of the movements of the tidal wave round Great Britain, in
order that we may understand the great diversity in the time of high
tide on any one day on different parts of the coast, and see how the
time of high tide for one part may be calculated from that of any other
locality.
Were it not for the inertia of the ocean and the resistance offered by
the irregular continents, high tide would always exist exactly under the
moon, and we should have high water at any place just at the time when
the moon is in the south and crossing the meridian of that place. But
while the inertia of the water tends to make all tides late, the
irregular distribution of the land breaks up the tidal wave into so many
wave-crests and greatly retards their progress.
Thus, the tidal wave entering the Atlantic round the Cape of Good Hope
mingles with another wave that flows round Cape Horn, and the combined
wave travels northward at the rate of several hundred miles an hour. On
reaching the British Isles it is broken up, one wave-crest travelling up
the English Channel, while another flows round Scotland and then
southwards into the North Sea.
The former branch, taking the shorter course, determines the time of
high tide along the Channel coast. Passing the Land’s End, it reaches
Plymouth in about an hour, Torquay in about an hour and a half, the Isle
of Portland in two hours and a half, Brighton in about seven hours, and
London in about nine hours and a half. The other branch, taking a much
longer course, makes its arrival in the southern part of the North Sea
about twelve hours later, thus mingling at that point with the Channel
wave of the _next_ tide. It takes about twenty hours to travel from the
south-west coast of Ireland, round Scotland, and then to the mouth of
the Thames. Where the two waves meet, the height of the tides is
considerably increased; and it will be understood that, at certain
points, where the rising of one tide coincides with the falling of
another, the two may partially or entirely neutralise each other.
Further, the flow and the ebb of the tide are subject to numerous
variations and complications in places where two distinct tidal
wave-crests arrive at different times. Thus, the ebbing of the tide may
be retarded by the approach of a second crest a few hours after the
first, so that the ebb and the flow do not occupy equal times. At
Eastbourne, for example, the water flows for about five hours, and ebbs
for about seven and a half. Or, the approach of the second wave may even
arrest the ebbing waters, and produce a second high tide during the
course of six hours, as is the case at some places along the Hampshire
and Dorset coasts.
Those who visit various places on our own coasts will probably be
interested in tracing the course of the tidal crests by the aid of the
accompanying map of the British Isles, on which the time of high tide at
several ports for the same time of day is marked. It will be seen from
this that the main tidal wave from the Atlantic approaches our islands
from the south-west, and divides into lesser waves, one of which passes
up the Channel, and another round Scotland and into the North Sea, as
previously mentioned, while minor wave-crests flow northward into the
Irish Sea and the Bristol Channel. The chart thus supplies the data by
means of which we can calculate the approximate time of high tide for
any one port from that of another.
[Illustration: FIG. 12.--CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE
ON DIFFERENT PARTS OF THE BRITISH COAST
_George Philip & Son. Ltd._ _The London Geographical Institute._]
Although the time of high water varies so greatly on the same day over
such a small area of country, yet that time for any one place is always
approximately the same during the same relative positions of the sun,
earth, and moon; that is, for the same ‘age’ of the moon; so that it is
possible to determine the time of high water at any port from the moon’s
age.
The time of high tide is generally given for the current year in the
local calendars of our principal seaports, and many guide-books supply a
table from which the time may be calculated from the age of the moon.
At every port the observed high water follows the meridional passage of
the moon by a fixed interval of time, which, as we have seen, varies
considerably in places within a small area of the globe. This interval
is known as _the establishment of the port_, and provides a means by
which the time of high water may be calculated.
Before closing this short chapter on the general characteristics of the
sea shore we ought to make a few observations on the nature of the water
of the sea. Almost everyone is acquainted with the saltness while many
bathers have noticed the superior buoyancy of salt water as compared
with the fresh water of our rivers and lakes. The dissolved salts
contained in sea water give it a greater density than that of pure
water; and, since all floating bodies displace their own weight of the
liquid in which they float, it is clear that they will not sink so far
in the denser water of the sea as they would in fresh water.
If we evaporate a known weight of sea water to dryness and weigh the
solid residue of sea salt that remains, we find that this residue forms
about three and a half per cent. of the original weight. Then, supposing
that the evaporation has been conducted very slowly, the residue is
crystalline in structure, and a careful examination with the aid of a
lens will reveal crystals of various shapes, but by far the larger
number of them cubical in form. These cubical crystals consist of common
salt (sodium chloride), which constitutes about three-fourths of the
entire residue, while the remainder of the three and a half per cent.
consists principally of various salts of magnesium, calcium, and sodium.
Sea salt may be obtained ready prepared in any quantity, as it is
manufactured for the convenience of those who desire a sea bath at home;
and it will be seen from what has been said that the artificial
sea-water may be prepared, to correspond almost exactly with that of the
sea, by the addition of three and a half pounds of sea salt to about
ninety-six and a half pounds of water.
This is often a matter of no little importance to the sea-side
naturalist, who may require to keep marine animals alive for some time
at considerable distance from the sea shore, while their growth and
habits are observed. Hence we shall refer to this subject again when
dealing with the management of the salt-water aquarium.
The attractions of the sea coast are undoubtedly greater by day than at
night, especially in the summer season, when the excessive heat of the
land is tempered by the cool sea breezes, and when life, both on the
cliffs and among the rocks, is at its maximum. But the sea is grand at
night, when its gentle ripples flicker in the silvery light of the full
moon. No phenomenon of the sea, however, is more interesting than the
beautiful phosphorescence to be observed on a dark summer’s night. At
times the breaking ripples flash with a soft bluish light, and the water
in the wake of a boat is illuminated by what appears to be liquid fire.
The advancing ripples, as they embrace a standing rock, surround it with
a ring of flame; while streaks and flashes alternately appear and
disappear in the open water where there is apparently no disturbance of
any kind.
These effects are all produced by the agency of certain marine animals,
some of which display a phosphorescent light over the whole surface of
their bodies, while in others the light-giving power is restricted to
certain organs or to certain well-defined areas of the body; and in some
cases it even appears as if the creatures concerned have the power of
ejecting from their bodies a phosphorescent fluid.
It was once supposed that the phosphorescence of the sea was produced by
only a few of the lower forms of life, but it is well known now that
quite a large number of animals, belonging to widely different classes,
play a part in this phenomenon. Many of these are minute creatures,
hardly to be seen without the aid of some magnifying power, while others
are of considerable size.
Among the peculiar features of the phosphorescence of the sea are the
suddenness with which it sometimes appears and disappears, and its very
irregular variations both at different seasons and at different hours of
the same night. On certain nights the sea is apparently full of living
fire when, almost suddenly the light vanishes and hardly a trace of
phosphorescence remains; while, on other occasions, the phenomenon is
observed only on certain patches of water, the areas of which are so
well defined that one passes suddenly from or into a luminous sea.
The actual nature of the light and the manner in which it is produced
are but ill understood, but the variations and fitfulness of its
appearances can be to a certain extent conjectured from our knowledge
of some of the animals that produce it.
In our own seas the luminosity is undoubtedly caused principally by the
presence of myriads of minute floating or free-swimming organisms that
inhabit the surface waters. Of these each one has its own season, in
which it appears in vast numbers. Some appear to live entirely at or
near the surface, but others apparently remain near the surface only
during the night, or only while certain conditions favourable to their
mode of life prevail. And further, it is possible that these minute
creatures, produced as they generally are in vast numbers at about the
same time, and being more or less local, are greatly influenced by
changes of temperature, changes in the nature of the wind, and the
periodic changes in the tides; and it is probable that we are to look to
these circumstances for the explanations of the sudden changes so
frequently observed.
In warmer seas the phenomenon of phosphorescence is much more striking
than in our own, the brilliancy of the light being much stronger, and
also produced by a greater variety of living beings, some of which are
of great size, and embrace species belonging to the vertebrates and the
higher invertebrate animals.
Those interested in the investigation of this subject should make it a
rule to collect the forms of life that inhabit the water at a time when
the sea is unusually luminous. A sample of the water may be taken away
for the purpose of examination, and this should be viewed in a good
light, both with and without a magnifying lens. It is probable, too,
that a very productive haul may be obtained by drawing a fine muslin net
very slowly through the water. After some time the net should be emptied
and gently washed in a small quantity of sea water to remove the smaller
forms of life contained, and the water then examined at leisure.
Of course it must not be assumed that all the species so obtained are
concerned in any way with the phosphorescence of the sea, but any one
form turning up in abundance when collected under the conditions named
will probably have some connection with the phenomenon.
One may well ask ‘What is the use of this light-emitting power to the
animals who possess it?’ but this question is not easily answered. The
light produced by the glow-worm and other luminous insects is evidently
a signal by means of which they call their mates, and this may be the
case with many of the marine luminous animals, but it is evidently not
so with those which live in such immense numbers that they are simply
crowded together; nor can it be so with the many luminous creatures
that are hermaphrodite. It is a fact, however, that numbers of deep-sea
species possess the power of emitting light to a striking extent; and
the use of this power is in such cases obvious, for since the rays of
the sun do not penetrate to great depths in the ocean, these luminous
species are enabled to illuminate their own surroundings while in search
of food, and, in many cases at least, to quench their lights suddenly at
such times as they themselves are in danger.