MARINE SURVEYING.
Modern engineers who have practised only under the benign reign of
Ordnance Surveys and Admiralty Charts, can have no idea of the toil
their predecessors underwent in procuring data for their designs and
reports; and I am safe in saying that Mr. Stevenson was of all others
the engineer to whom in his sea coast practice, such useful aids would
have been of the very highest value.
For example, before he could tell, with the exactness he desired, the
distance between the Bell Rock Lighthouse and the shore, he had, in
absence of any reliable information, to undertake a pretty extensive
trigonometrical survey of the coast, involving the measurement of
a _base line_ upwards of two miles in length--a most “laborious
operation,” he observes, in which his assistants were aided by six
sailors from the lighthouse tender.
Again, to show the difficulty in determining the best site for a
lighthouse in those early days, before an accurate Government survey of
the coast line had been made, I give from Mr. Stevenson’s Journal the
following notes of his observations to determine the best site for a
lighthouse at Kinnairdhead in Aberdeenshire. I give them _at length_,
as jotted down at the time, for they may perhaps lead young engineers
of the present day to be thankful that, in most cases at least, they
are not, from want of accurate coast surveys and soundings, left to
resort altogether to their own resources in getting the information
they require. But I think they are specially worthy of record as
showing the extreme care bestowed by Mr. Stevenson in getting the
data to enable him to determine the exact positions of the several
lighthouses _he designed_. His Journal says:--
“_First._--I caused a mast to be erected upon the top of
Kinnairdhead Castle or Lighthouse, making its extreme height from
the ground 100 feet.
“Got the yacht under weigh, and having a careful pilot on board, I
sailed for Rattray Head, and there observed the mast over the land
of Cairnbulg, it being then high water, or twenty minutes past 7
P.M. With the parapet of the lighthouse in view, have eight fathoms
water off the head, which bore W.N.W. Run in upon the head with
flag upon the mast seen over the land till seven fathoms water,
when the flag disappeared. Then leave the vessel and sound from the
boat, and have 6 fathoms, 5, 5, 4¼, 3, 2, 1 fathom, and lastly 3½
feet. Return to the ship in a more southerly direction, and have 3
feet, 1 fathom, 2, 2¼, 2¾, 3½, 4, 4¾, 5, 5½, 6½, and 7 fathoms. All
these soundings rocky bottom.
“With the Windmill near Peterhead on with Stirling hill, and
Monument hill on with the rounded Sandy Down of Rattray, and the
parapet of Kinnairdhead Lighthouse seen over Cairnbulg land, you
are in 8 fathoms water off Rattray Briggs, which lie about ¼ of a
mile to the southward of the Sandy Down.
“Wait off the Briggs till the light was seen, then stood in upon
the Briggs till the light was shut in by the land of Cairnbulg, and
at that moment had 8 fathoms water, so that at present the light
forms an excellent direction for Rattray Briggs.
“Find that the lightroom is seen fully from the yacht’s deck in 8
fathoms water off Rattray Briggs, that the flag upon the masthead
is seen in 6 fathoms water--high water spring tides. Ship then
bearing from the head E.S.E. and W.N.W., distant about one mile
from the shore, where a man is distinctly observed at a boat in the
twilight.
“_Secondly._--Remove the mast from the castle or lighthouse on the
morning of the 15th to Cairnbulg, and elevate a flag to the height
of 86 feet from the ground, or 97 feet from high water mark, at the
distance of about 100 yards from the high water mark at the point
connected with Cairnbulg Briggs.
“The yacht lying off or to the westward of the Briggs, was got
under weigh at 2 A.M. of the 16th, and beat up the north shore
as far as Rosehearty, and there observed the flag over the land.
Found off Rosehearty that the flag was just hid by the highest
inequalities of the land to the southward of the Castle, and
that it appeared at the lower or flat places sometimes in sight
20 feet above the land, and at other places intercepted by the
land and houses of the town, amongst which it often appeared and
disappeared. The range of the flag along the land was as far as Mr.
Dalrymple’s house when it was time to put about, having there three
fathoms at nearly low water.
“After completing the observations in this direction, sailed along
the shore southwards to Rattray Briggs. Find that Inverallochy
head, south-eastward of the town of Cairnbulg, is the eastmost
point on this coast, but, being at a distance from the foul ground
of Cairnbulg, would make a less desirable point than Cairnbulg.
“Off Rattray, in eight fathoms water, begin to lose sight of
the lantern on Kinnairdhead Castle as before. See the mast and
flag at Cairnbulg a considerable way up the country over the
lands of Inverallochy. See the flag, standing in upon Rattray
to five fathoms water at half tide, lose it, and then stand for
Fraserburgh.
“As the result of these trials, find that Inverallochy head or
point is the most eastern or projecting point of land upon that
coast, that Cairnbulg is the next projecting point. The former lies
between the points of danger, viz., Rattray and Cairnbulg.
“Find that if the light were to be moved to a more southern
situation, it would be better on either of the above places than
Rattray Head, which would entirely remove its usefulness from the
Moray Firth.
“Find that in the event of two lights for this coast, the one
ought to be at Kinnairdhead, and the other upon the Cock Inch at
Peterhead.
“Under all the circumstances of the case, find that it would be
most advisable to erect a new lighthouse at Kinnairdhead, about
100 yards more to the eastward than the Castle stands, and erect
it about twenty or thirty feet higher than the Castle. This, with
a better light, would perhaps answer the general purposes of
the coast better than a single light placed on any of the other
stations along this coast.”
After perusing this extract, the reader, I think, will not be surprised
to find Mr. Stevenson making an urgent appeal on behalf of all
interested--Seamen--Fishermen, and Engineers, for a Government Survey
and “Sailing Directions” of the intricate navigation of the shores of
Scotland, which he did in the following terms:--
“The attention which Government has long paid to the improvement
of the Highlands and Islands of Scotland, in connection with the
British Fisheries, has been attended with the best effects in the
country at large. It is much to be wished that these shores were
rendered more accessible to the mariner.
“The marine survey of the Highlands by Murdoch Mackenzie,
undertaken by order of the Lords of the Admiralty, may be
considered as the first grand step towards the improvement of the
Highlands, and next to that the later institution of the Northern
Lighthouses. By means of these the fisher may find his way from
loch to loch, and the mariner bound over seas, instead as formerly
of holding a course without the Lewis Islands, can now find his
way through the Sounds, and in adverse winds take shelter in safe
harbours, instead of being exposed to the boisterous seas of the
Atlantic Ocean; these charts and lighthouses have in many points
of view contributed to the improvement of the Highlands, and to
the present flourishing trade carried on through these Sounds from
Liverpool, etc., to the northern continent of Europe. However, from
the extensive range of coast which these charts include, together
with the prodigious number of extensive lochs and small islands, it
was impossible that any first survey could be made so accurate as
to supply the place of pilots, where there are neither landmarks
to characterise the coast, nor beacons or buoys to point out the
situation of sunk rocks; and although these charts have certainly
contributed much to the facility and security of the navigation
of the Highlands, yet no one will say that they are free from
imperfections, and their incommodious size and high price are
insurmountable bars to their general utility, thereby rendering
them impracticable for the use of small vessels, so that they
are only to be found in the cabins of large vessels, where large
accommodation affords room to unfold them, but even here also the
price forms an objection, as the charts are always _found_ by the
shipmaster.
“Nothing therefore can be more necessary or essential to the
improvement of the Highlands and Islands of Scotland, than an
accurate survey of the fishing grounds, lochs, and harbours, upon
a scale considerably larger than Mackenzie’s charts, given in the
form of a book of the size of a large quarto, containing only the
lochs, etc., interleaved with printed directions and descriptions
of each chart or harbour, which book of charts, accompanied with a
general chart would sufficiently guide the mariner and fisher in
their several pursuits.
“With regard to an accurate survey of the lochs and harbours
in the Highlands published in the most commodious form for the
use of small vessels, such an undertaking would require to be
sanctioned in a manner similar to the survey undertaken by Murdoch
Mackenzie, and though in process of time the sale of these charts
might produce a considerable return to those concerned with it,
yet the time and attention which such (with a laborious number of
soundings) must occupy would certainly require that those concerned
in the undertaking should be put in possession of certain sums
of money to enable them to go on with that deliberation which is
essential to accuracy, and this encouragement should be the more
considerable that the charts might be procured to the public at a
moderate price.”
This Memorial, written in 1803, was intended for and in some shape
communicated to the Admiralty, and was followed by good results.
In “A Memoir of the Hydrographical Department of the Admiralty,”
published in 1868,[13] are the following remarks:--“It was about this
time,” 1810, “that the Admiralty first conferred on the Hydrographer
the privilege of selecting a surveyor for the _home coasts_. Singular
as it may appear, the Hydrographer had at this time great difficulty
in finding a naval officer competent to fill the position, or who
was acquainted with anything beyond surveying by common compass. At
length, however, about 1811, Mr. George Thomas, a master, was selected”
for home service. The Memoir also states that at the same time the
Hydrographer appointed to foreign service Mr. Beaufort, afterwards
Sir Francis Beaufort, the eminent Hydrographer to the Admiralty,
who was, all his life, Mr. Stevenson’s intimate friend and constant
correspondent.
There is therefore, I believe, no reason to doubt that Mr. Stevenson’s
original appeal and subsequent personal friendly and free intercourse
with the officials of the Admiralty led to the establishment, on a
_systematic footing_, of our Government “Admiralty Survey,” which, as
all engineers know, indicates with marvellous accuracy and detail every
shoal, sunken rock, and sounding on the coasts of Great Britain and
Ireland; and from which the “Admiralty Sailing Directions” have been
prepared with such discernment and care that the whole system of our
coast survey may now be said to have attained perfection.
With Colonel Colby, also, of the Royal Engineers, who was Director
of the Ordnance Survey, Mr. Stevenson regularly corresponded, being
no less interested in the progress of the great national work so
successfully carried on under his charge.