Fune 24, 1886] 
NATURE 
181 
special class of questions and become experts in all that relates 
to fishery problems. 
Further, is it desirable that the matters which are to be 
inquired into should be determined by an official unskilled in 
natural history? Or, onthe other hand, that the selection of 
inquiries likely to lead to a satisfactory result should be made 
by a man of science, specially conversant with the nature of the 
things to be dealt with ? 
The organisation required consists, 
concerned, of :— 
(1) A chief scientific authority. 
(2) A staff of working naturalist-inspectors. 
(3) A staff of clerks. 
And, so far as material is concerned, of :— 
(4) A London office, with collection of fishes, apparatus used 
in fishing, maps, survey-records, statistical returns, and library. 
(5) A surveying-ship, under the orders of the Department, to 
be manned and maintained by the Admiralty. 
(6) A chief laboratory fitted for carrying on investigations 
such as those named in Section II., and also two smaller moy- 
able laboratories, together with steam yacht fitted for dredging 
and sounding. 
(7) Hatching-stations and fish-ponds. 
With regard to the foregoing headings, it is a matter for con- 
sideration whether ‘‘the chief scientific authority” should be 
an individual or a committee of five. The position assigned 
to this post should be equal to that of the Director of the 
Geological Survey or the Director of the Royal Gardens, Kew, 
or, if the ‘‘ authority” takes the form of a committee, it should 
be placed on the same footing as the Meteorological Council. 
The person or persons so appointed should be responsible for 
all the operations of the Department, and of such scientific 
training and capacity as to be likely to devise the most useful 
lines of inquiry and administration. 
The ‘‘naturalist-inspecters”’ should be six in number, but 
operations might be commenced with a smaller staff. They 
should be thoroughly competent observers, and under the direc- 
tion of the chief scientific authority they would be variously 
employed, either on the surveying-ship, at the chief laboratory, 
or in local laboratories, hatching-stations, or in the London 
office and museum. 
The naturalists thus employed would become specialists in 
all matters relating to the life-history of fishes and their food ; 
they would acquire a skill and knowledge far beyond that which 
it is possible to find amongst existing naturalists, who occa- 
sionally are requested to make hurried reports on such matters 
as salmon disease or the supposed injury of the herring-fisheries 
by trawlers. 
One of the naturalist-inspectors should be a chemist and 
physicist, in order to report on the composition of the water 
and the nature of the bottom in the areas investigated. 
“Clerks” would be required in the London office to tabulate 
statistics and carry on correspondence. These gentlemen need not 
necessarily have any scientific knowledge. It would probably be 
necessary to have a correspondent or agent of the Department in 
every large fishing centre. Probably the coast-guard officials 
might be taken into this service. 
With regard to material equipment it appears to be necessary 
that a Scientific Fisheries Department should have at its 
London office a Museum of fishing apparatus for reference and 
instruction, and also complete collections illustrative of the 
fishes, their food, enemies, and other surroundings. In the 
same building would be exhibited maps showing the distribu- 
tion and migrations of food-fishes, the coast temperature and 
its variations, the varying character of the sea-bottom, sea- 
water, &c. 
The surveying-ship or ships would be provided by the 
Admiralty. 
A central laboratory is in course of erection upon Plymouth 
Sound by the Marine Biological Association. Her Majesty’s 
Government has promised to contribute 5000/. and 500/, a year 
to this institution, on condition that its resources are avail- 
able for the purpose here indicated. Certain of the ‘‘ natur- 
alist-inspectors” (probably three at any one time) would 
be stationed at the Plymouth laboratory in order to carry on 
pce studies of the development and food of particular species 
of fis 
The smaller movable laboratories, steam-yacht, 
appliances would not be costly. 
so far as persons are 
and other 
ON NEW APPLICATIONS OF THE MECHANI- 
GAL PROPERTIES OF GORKG MOS RAE ARTS + 
i would seem difficult to discover any new properties in a 
substance so familiar as cork, and yet it possesses qualities 
which distinguish it from all other solid or liquid bodies, namely, 
its power of altering its volume in a very marked degree in con- 
sequence of change of pressure. All liquids and solids are 
capable of cubical compression, or extension, but to a very small 
extent ; thus water is reduced in volume by only 1/2000 part 
by the pressure of one atmosphere. Liquid carbonic acid yields 
to pressure much more than any other fluid, but still the rate is 
very small. Solid substances, with the exception of cork, offer 
equally obstinate resistance to change of bulk; even india- 
rubber, which most people would suppose capable of very con- 
siderable change of volume, we shall find is really very rigid. 
I have here an apparatus for applying pressure by means of a 
lever. I place a piece of solid india-rubber under the plate and 
you see that I can compress it considerably by a very light pres- 
sure of my finger. I slip this same piece of india-rubber into a 
brass tube, which it fits closely, and now you see that [am 
unable to compress it by any force which I can bring to bear. I 
even hammer the lever with a mallet, and the blow falls as it 
would on a stone. The reason of this phenomenon is, that in 
the first place, with the india-rubber free, it spread out laterally 
while being compressed longitudinally, and consequently the 
volume was hardly altered at all ; in the second case, the strong 
brass tube prevented all lateral extension, and because india- 
rubber is incapable of appreciable cubical compression, its 
length only could not be sensibly altered by pressure. 
Extension, in like manner, does not alter the volume of india- 
rubber. In this glass tube is a piece of solid round rubber which 
nearly fills the bore. The lower end of the rubber is fixed in 
the bottom of the tube, and the upper end is connected by a fine 
cord to a small windlass, by turning which I can -stretch the 
rubber. I fill the tube to the brim with water, and throw an 
image of it onto the screen. If stretching the rubber either 
increases or diminishes its volume, the water in the tube will 
either overflow or shrink in it. I now stretch the rubber to 
about 3 inches, or one-third of its original length, but you can- 
not see any appreciable movement in the water-level, hence the 
volume of the rubber has not changed. 
Metals when subjected to pressures which exceed their elastic 
limits, so that they are permanently deformed, as in forging or 
wire-drawing, remain practically unchanged in volume per unit 
of weight. 
I have here a pair of common scales. To the under sides of 
the pans I can hang the various specimens that I wish to examine ; 
underneath these are small beakers of water which I can raise 
or lower by means of a rack and pinion. Substances immersed 
in water lose in weight by the weight of their own volume of 
water ; hence if two substances of equal volume balance each 
other in air, they will also balance when immersed in water, 
but if their volumes are not the same, then the substance having 
the smaller volume will sink, because the weight of water it 
displaces is less than that displaced by the substance with the 
larger volume. To the scale on your left hand is suspended a 
short cylinder of ordinary iron, and to the right-hand scale a 
cylinder of ordinary copper. They balance exactly. I now 
raise the beakers and immerse the two cylinders in water; you 
see the copper cylinder sinks at once, and I know by that that 
copper has a smaller volume per pound than iron, or, as we 
should com:ronly say, it is heavier than iron. I now detach 
the copper cylinder, and in its place hang on this iron one, 
which is made of the same bar as its fellow cylinder, but forced, 
while red hot, into a mould by a pressure of sixty tons per 
square inch and allowed to cool under that pressure. The two 
cylinders balance, as yousee. Has the volume of the iron in 
the compressed cylinder been altered by the rough treatment it 
has received? I raise the beakers, immerse the cylinders, the 
balance is not destroyed ; hence we conclude that although the 
form has been changed the volume has remained the same. I 
substitute for the hot compressed cylinder one pressed into a 
mould while cold, and held there for some time, with a load of 
sixty tons per square inch ; the balance is not destroyed by 
immersion, hence the volume has not been altered. I can 
repeat the experiments with these copper cylinders and the 
* A Paper read at the Royal Institution of Great Britain on April 9, 1886, 
by William Anderson, M.Inst.C.E., M.R.I. 
