solution, is an acid infusion of red cabbage. For its preparation,
one or more red cabbages should be cut into strips, and boiling
water poured upon the pieces; a little dilute sulphuric acid is to
be added, and the whole well stirred: it is then to be covered and
kept hot as long as possible, or, if convenient, should be heated
nearly to boiling, for an hour or two, in a copper or earthen
vessel. The quantity of water to be added at first should be
sufficient to cover the cabbage, and the sulphuric acid should be
in the proportion of about half an ounce of strong oil of vitriol
by measure to each good-sized plant. This being done, the fluid
should be separated and drained off, and as much more hot water
poured on as will cover the solid residue, adding a very little
sulphuric acid. The whole is to be closed up, and suffered to
stand until cold, and then the liquid poured off and added to the
former infusion. The cabbage may now be thrown away. The infusion
is to be evaporated to one half or one third its first bulk, poured
into a jar, allowed to settle, and the clear red fluid decanted
and preserved in bottles. The residue may have water added to
it, the solid part be allowed to subside, the clear liquor drawn
off, evaporated and added to the former, or it may be dismissed
altogether. This solution will keep for a year. When [p279] required
for use, the acid of a small portion of it should be neutralized
by caustic potash, or soda, (not by ammonia,) when it will assume
an intensely deep blue colour, and will, in most cases, require
dilution with twelve or fourteen parts of water. The red liquor of
pickle cabbage will, occasionally, answer the uses of the solution,
and is, when required for service, to be neutralized in a similar
manner.”
For test-papers, litmus and turmeric are the most essential, and
several precautions in preparing and using them are here pointed out,
which, though apparently trivial, are, in fact, extremely important
in insuring correct conclusions. We transcribe a part of the account
of the applications of these coloured papers, as a specimen of the
clear minuteness with which the details of the work are given, and as
a sample of the author’s general method and style, where subjects of
much greater intricacy are to be explained.
“591. In using these test papers with a fluid suspected to contain
free acid or alkali, or knowing that one of these substances is
predominant, to ascertain which is so, all that is necessary is to
moisten them with the liquid, and observe the change: if the fluid
be acid, the blue colour of the litmus will immediately become red;
if alkaline, the yellow colour of the turmeric will be changed to a
brown. The moistening may be effected by dipping the paper into the
liquid; but a better method is to touch the edge of the slip with
a rod dipped in the fluid. In the latter case there is no risk of
contamination to the fluid from the paper, and only a very minute
quantity of the liquid is used at once.
“592. These trials must be made by day-light; artificial light not
permitting that just estimation of the changes by which the presence
of a small excess of acid or alkali is to be determined. As the
proportion of free acid or alkali diminishes, the intensity of the
new tint produced upon the paper is also diminished; and when in
very small quantity, it requires considerable attention before a
decision can be arrived at. The test paper should occasionally be
touched with pure water in the immediate neighbourhood of the part
where the solution has been applied, for any change in appearance
that may have occurred, not due to mere moistening, is then readily
perceived.
“593. Although acid is generally tested for by litmus paper,
and alkali by turmeric paper, yet the former is sometimes used
advantageously for the latter purpose, being first slightly
reddened, either by exposure to the air, or by momentary contact
with muriatic acid fumes. When the [p280] paper thus modified is
used to detect a free alkali, instead of turmeric paper, that
substance is indicated by the restoration of the original blue
colour. Litmus paper is best slightly reddened for this use, by
putting a drop or two of muriatic acid into a large jar, allowing
it to stand a few minutes, and then bringing the paper towards the
mouth of the jar, or carefully placing it within: so soon as the
blue tint has become slightly reddened, the paper should be removed
for use. If too much acid be imparted to the paper, the delicacy
of its indications is injured, because of the greater quantity of
alkali required to neutralize the acid, and restore the blue colour.
For the same reason a paper free from alkali or carbonate of lime
has been recommended for the preparation of these tests: for these
impurities, combining with a minute portion of acid, neutralize it,
and thus prevent that delicacy of indication which the test paper
ought and may be made to possess.”
The mode of determining the value of alcaline substances, or
“alcalimetry,” is described at length in this section. Our readers,
however, will here recollect that there is an error respecting the
specific gravity of the acid, which Mr. Faraday has corrected at page
221 of the present volume of this Journal. The thirteenth section
is allotted to crucible operations, and the fourteenth to furnace
tube operations. They are full of minute and admirable instructions,
evidently deduced from long experience, and detailed with the
same precision and clearness which we have already eulogised. The
fifteenth section, which occupies nearly a hundred pages, relates to
“pneumatic manipulation, or management of gases.” Every paragraph of
the instructions here given will be found to contain something of
importance to the student; it is, indeed, a valuable essay upon a
difficult and nice department of chemical research.
Under the head “Tube Chemistry,” in the sixteenth section, a
variety of means are pointed out, of working with and employing
glass-tubes, as substitutes for more expensive and formal apparatus.
Indeed, the young chemist cannot do better than practise the art of
bending, drawing out, and sealing tubes, as here directed, (and in
the nineteenth section,) by which he will soon gain the requisite
dexterity in forming them into test tubes, retorts, and so on, and
be enabled to furnish his laboratory with a quantity of very useful
vessels and apparatus, at a very moderate expense.
The application of electricity to chemical purposes forms the subject
of the seventeenth section, in which the [p281] management of
electrical machines and apparatus is described, and the circumstances
necessary to facilitate investigation and insure success are pointed
out. To this succeed the management and composition of lutes, and a
chapter on bending blowing, and cutting glass.
Cleanliness, order, and regularity are of the utmost importance in
the laboratory; and though the appearance of the chemist himself
is often such that he appears “to doat upon dirt,” the strictest
nicety must generally be observed in the state of his utensils and
apparatus. These matters must, indeed, generally engage his personal
attention; and it is not sufficient that glasses and other vessels
be merely washed and wiped in the usual way, but they are generally
required to be free from the minutest portions of adhering matter.
A section is accordingly appropriated to the subject of cleanliness
and cleansing, in which, and in that which follows it, entitled
“General Rules for young Experimenters,” much information is conveyed
that will prove useful to those who are commencing the practice of
experimental inquiries in chemistry, and also to such as, having made
some progress, have indulged themselves in slovenly habits. Macquer’s
observations on this subject, as quoted by our author, are so much
to the purpose, and so well deserving the serious attention of the
young chemist, that we shall stand excused for inserting them in this
place. He says, “A persuasion must exist that arrangement, order,
and cleanliness, are essentially necessary in a chemical laboratory.
Every vessel and utensil ought to be well cleansed as often it is
used, and put again into its place; labels ought to be attached to
all the substances, mixtures, and products of operations which are
preserved in bottles or otherwise; these should be examined and
cleansed from time to time, and the labels renewed when required.
These cares, although they seem to be trifling, are, notwithstanding,
the most fatiguing and tedious, but the most important, and often the
least observed. When a person is keenly engaged, experiments succeed
each other quickly; some seem nearly to decide the matter, and
others suggest new ideas; he cannot but proceed to them immediately,
and he is led from one to another; he thinks he shall easily know
again the products of his first experiments, and therefore he does
not take time to put them in order; he prosecutes with eagerness
the experiments which he has last thought of, and in the mean time
the vessels employed, the glasses and bottles filled, so accumulate
that he cannot any longer distinguish them; or at least he is [p282]
uncertain concerning many of his former products. This evil is
increased, if a new series of operations succeed, and occupy all the
laboratory; or if he be obliged to quit the place for some time,
every thing then goes into confusion. Hence it frequently happens
that he loses the fruits of much labour, and that he must throw away
almost all the products of his experiments.
“The only method of avoiding these inconveniences is to employ the
cares and attentions, above mentioned. It is indeed unpleasant
and very difficult continually to stop in the midst of the most
interesting researches, and to employ much valuable time in cleaning
and arranging vessels and attaching labels. These employments are
capable of cooling and retarding the progress of genius, and are
tedious and disgusting; but they are nevertheless necessary. Those
persons whose fortunes enable them to have an assistant operator,
on whose accuracy and intelligence they can depend, avoid many of
these disagreeable circumstances; but they ought nevertheless to
attend to the execution of these things. We cannot depend too much
on ourselves in these matters, however minute, on account of their
consequences. This becomes even indispensable when the experiments
are to be kept secret, at least for a time, which is very common and
often necessary in chemistry.
“When new researches and inquiries are made, the mixtures, results,
and products of all the operations ought to be kept a long time
well ticketed and noted. It frequently happens that at the end of
some time these things present very singular phenomena, which would
never have been suspected. There are many beautiful discoveries
in chemistry which were made in this manner, and certainly a much
greater number which have been lost, because the products have been
thrown away too hastily, or because they could not be recognised
after the changes which happened to them.”
The uses of equivalents, and the method of employing Dr. Wollaston’s
scale, form the subject of the twenty-second section of Mr. Faraday’s
book; and of the concluding sections, the twenty-third contains
a quantity of miscellaneous remarks, and the twenty-fourth is
appropriated to “a course of inductive and instructive practices;”
that is, to a selection of minute instructions respecting the use of
instruments, and the performance of operations.
Such is an outline of the contents of this volume, of which we
have felt ourselves obliged to speak in terms unequivocally [p283]
favourable; in fact, it contains, strictly speaking, nothing to
criticise. It is minute, laborious, and very unpretending, and
contains a body of instructions for the performance of experiments,
and of descriptions of the modes of managing and applying apparatus,
which is not to be had elsewhere, being manifestly derived from
diligent research, extensive experience, and correct judgment. It
is not a book for amateurs; for they will presently learn from it
that there is no royal road to the science of which it treats; but
the real student, who will seriously follow its laborious details,
will discover in them an acceptable and sure guide through the
crooked and intricate, as well as the straight paths of chemistry.
Those, however, and those only, who are well versed in the business
of the laboratory, both as experimentalists and teachers, can duly
appreciate the weighty service which Mr. Faraday has here performed.
_Statistical Notices suggested by the actual State of the British
Empire, as exhibited in the last Population Census_. Communicated by
Mr. Merritt.
[Read before the Literary and Philosophical Society of Liverpool.]
The population returns of the _decennial lustrum_, or period of
ten years, which ended in 1821, were delayed for a considerable
time, on account of the difficulties which have always occurred in
taking the population of Ireland. They have now, however, been some
time completed, and from the _data_ they afford, a few reflections
naturally present themselves, which though sufficiently obvious, yet,
from the extreme interest of the subject, may be thought deserving
of being brought together, and exhibited in a connected form. They
point out some peculiarities in the situation of this country, which
distinguish it from almost every other nation that has yet existed in
ancient or modern times.
From the notices which have been published respecting the different
districts, it may be inferred, that the portion which may be termed
the _Urban_ population, has augmented in a much greater degree
than the _Rural_. The general ratio of increase has, however, been
very great, and, in the opinion of Mr. Malthus, still continues at
the same rate. That eminent [p284] economist has lately given it
as his opinion, before the Emigration Committee, that the present
inhabitants of the British Islands do not amount to less than
twenty-two millions and a half. This estimate is perhaps a little
exaggerated; but as it may be assumed sufficiently near the truth for
all the objects of general speculation, I shall proceed to point out
a few of those leading peculiarities, to which I have just alluded.
In the first place we may assert, I apprehend, on sufficient grounds,
that Great Britain is the most populous nation which has existed
since the Christian era. No other instance has occurred in which an
extent of continuous surface of 93,000 square miles has sustained
a population of twenty-two millions. Italy, which is not of much
greater extent, has sometimes been rated at nearly the same amount,
but this estimate has been formed in the absence of all actual
enumeration and is now ascertained to be a considerable exaggeration.
No other part of the world can enter into the competition, unless it
be certain districts of China and Japan, but which, as our knowledge
of them in this respect is quite uncertain, I shall leave wholly out
of the question. How far some nations of the ancient world may have
approached or gone beyond us in the race of population, is perhaps
equally lost in uncertainty. There is reason to believe, as I have
endeavoured to demonstrate on another occasion, that some districts
of the old world exceeded, in this respect, any country of modern
ages. Amongst them, perhaps, may be reckoned Egypt, Mesopotamia,
the lesser Asia, and some parts of Persia: but certainly, neither
in ancient nor modern times do we find any instance of a single,
compact, distinct empire, exactly defined, identically governed, and
peopled by twenty-two millions of souls on the same extent of soil;
this is undoubtedly a peculiarity the most striking which can exist
among nations.
In the second place, we may, I think, affirm with tolerable
certainty, that no nation ever contained so many large cities. On
this point Great Britain exhibits a splendid superiority. We have
two cities of the first class, London and Dublin; the one with a
population of more than a million, the other with little less than
three hundred thousand. Of cities of the second class, or those which
reach one hundred thousand inhabitants, [p285] or above that number,
we have seven, _viz._, four in England, Manchester, Liverpool,
Birmingham, Bristol; two in Scotland, Edinburgh and Glasgow; and
one in Ireland, the city of Cork. These seven average considerably
more than one hundred thousand each. We have fourteen towns of the
third class, or those containing from thirty to fifty thousand
or upwards of inhabitants, _viz._, ten in England: Portsmouth,
Plymouth, Norwich, Leeds, Sheffield, Nottingham, Bath, Newcastle,
Coventry, and Hull. Two in Scotland, Paisley and Dundee, and two
in Ireland, Belfast and Limerick. Of towns of the fourth class, in
which are usually reckoned those of from fifteen to thirty thousand
inhabitants, we have at least thirty, and probably more. A slight
glance at the principal nations of Europe, with this view, will show
at once their immense inferiority.
To begin with France, the most populous of the great sovereignties.
That empire possesses only one city of the first class, _viz._ Paris,
which is inferior to London by one third. She has five of the second
class, _viz._, Lyons, Bourdeaux, Marseilles, Lisle and Rouen; but,
according to the latest information which I have been able to obtain,
they will not reach, by a very considerable proportion, the average
number of the seven English cities of the same class. France has also
eight towns of the third class, _viz._, Amiens, Caen, Nantes, Brest,
Toulouse, Toulon, Mentz, and Versailles. I am not quite sure, as no
census has lately been taken, whether two or three of the following
towns ought not to be included in this class, though I am inclined,
on the whole, to a contrary opinion, _viz._, Melun, Montpelier,
Nanci, Dijon, Tours, Rennes, and Troyes; they will not, however, I am
persuaded, come near the average of the British third-rate towns. The
same remark will hold as to the number and size of the inferior towns.
With respect to the rest in rank of the great monarchies, the
Austrian Empire, a very few words will suffice, as it cannot pretend
to come into any competition with us, on the point in question.
Austria possesses only one city of the first class, and three of the
second, _viz._, Vienna, Prague, Milan, Venice. The towns of the third
rank are proportionably few. With Spain, Russia, and Prussia, it
would be idle to enter into any comparison. [p286]
It must be confessed, however, that the present kingdom of the
Netherlands, as established by the congress of Vienna contains,
in proportion to its extent and population, more large towns than
any single state which now exists, or perhaps has ever existed.
With an extent of territory and number of inhabitants scarcely
exceeding, one-fourth of the British dominions, that kingdom has one
city the first class, Amsterdam; two of the second rank, Rotterdam
and Brussels; and probably as many of the third class as Great
Britain herself. But the Kingdom of the Netherlands is in itself
too insignificant to enter into any competition with such a state
as Great Britain for any objects of general comparison. The various
states comprehended under the common geographical appellation of
Italy, if that superb country was united under one head, is the
only one of the European nations which, under the view we are now
considering, could sustain any parallel with Great Britain. But
this union, so desirable in many points of view, would probably
diminish its pretensions as a nation of large cities. Many of these
have reached their present grandeur and extent by having been long
the seat of a court or a government, and would perhaps decline
considerably if reduced to the rank of mean provincial capitals. But
even under any circumstances of territorial union, Italy could not
be held to comprize more than one city of the first class, _viz._,
Naples, and six of the second, _viz._, Turin, Milan, Venice, Genoa,
Florence, and Rome; whereas, as we have just seen, Britain has two
of the first and seven of the second, and these superior in size and
number of inhabitants.
The third peculiarity which I have to remark in the actual situation
of the British dominions is, that no nation ever had so great an
_urban_ population, or so large a proportion of its inhabitants
residing in towns. This peculiarity is intimately connected with
that which I have just described; but it is nevertheless a very
different characteristic. Great Britain is not only distinguished for
the number and size of her large cities, but for having so _great_
a number of them on so _small_ a territory. By the census of 1811,
it was found that nearly half our population resided in towns, and
at present, I apprehend, the proportion will be found still greater.
In this [p287] respect no nation has ever approached us. The French
economists were of opinion that not more than one-fourth of the
people of France lived in towns; and the later statists, who have
alluded to the subject, contend that a still greater proportion of
the population is rural. This will not appear exaggerated when it
is recollected that all the lower classes of that country subsist
principally on vegetable food, and that, consequently, the greater
part of the soil being under tillage, a great number of hands is
required for its cultivation. In Great Britain, on the other hand,
the inhabitants of all classes consume a great quantity of animal
food, and, of course, a great part of our lands, being in a pastoral
state, require a small proportion of occupants. In the kingdom of the
Netherlands, it is supposed about one-third of the inhabitants live
in towns: in Italy about one-fifth: in Austria, Spain, and Russia,
except the province of Siberia, where the abundance of manufactures
congregates the people in masses, not more than one-fifth. In Russia,
Sweden, and Norway, where, amongst the lower classes, nearly every
family is its own manufacturer, not more than one-eighth or one-ninth.
The fourth and last of these peculiar characteristics which I shall
remark, is, that no great nation ever employed so large a proportion
of its people in trade and manufactures. In speaking thus, I leave
out of the question the Italian and Flemish republics of the middle
ages, and the Hanse Towns, free cities, and United Provinces of later
times. I speak only of great and extensive countries. It will appear,
I doubt not, by the present census, that at least half our whole
population is employed in trade, commerce, or manufactures. This is a
feature altogether singular; a circumstance to which no parallel can
be found in the ancient or modern world.
From these premises, a few observations, in the way of corollaries,
will naturally suggest themselves.
In the first place, such a state of things is indicative of great
wealth and power. A country thus situated is, beyond any other,
powerful for attack and strong for defence. A profusion of great
cities can only be produced by extensive trade, and can only be
maintained by a highly cultivated soil. The wealth acquired by
the industry of the towns, reacts on the [p288] industry of the
agriculturist, and it is in this that the real advantages of commerce
primarily consist. In this way an extensive population is gradually
generated, for no maxim or political economy is now more generally
admitted, than that population is sure to follow close and to press
hard against the means of subsistence. An affluence of inhabitants on
a comparatively small territory, is, itself the primary ingredient
of power, and this first requisite of strength is, in the case of
Great Britain, essentially corroborated by our insular situation.
Surrounded by dangerous coasts and tempestuous seas, we can only be
approached at certain points and certain times; whilst, on the other
hand, as this state of things supposes and supports a powerful navy,
we are able in a great degree to choose our point of attack.