128 

level ground, the potential energy acquired when the foot is 
lifted, and the consequent slight loss of heat, is neutralised by 
the izternaZ work necessary to prevent the foot having any actual 
energy at the moment it touches the ground. 
Upon this theory it is clear that the fall of temperature must 
be greater as the height arrived at is more considerable; and that 
the body must soon regain its normal temperature when the 
experimenter ceases to ascend. Lortet’s observations agree per- 
fectly with these requirements, he finding that his temperature 
was normal in less than half an hour after he had reached the 
summit. 
In descending a hill the temperature ought evidently to rise 
greatly if this explanation is the true one. 
A. H. GARRopD 
St. John’s College, Cambridge, December 3 

Hailstones 
I HAVE frequently observed that when hailstones are large and 
well formed, they are almost invariably round and smooth at one 
end, and roughly conical at the other (as in 
the annexed sketch), so as to suggest the idea 
that they are broken portions of sphcres, of a 
structure radiating from the centre. 
Perhaps some of your correspondents can 
inform me if there is any proposed theory 
which accounts for this peculiar form, which 
should throw some light on the formation of hail. 
H. R. PROCTER 

Clementhorpe, North Shields 

ENCOURAGEMENT TO NATURAL SCIENCE 
AT TRINITY COLLEGE, DUBLIN 
terete have from time to time appeared in this 
journal of scholarships, exhibitions, &c., obtainable in 
various colleges at Oxford and Cambridge, for proficiency 
in the purely Natural Sciences. From these we see that 
the neglect with which the study of nature has been treated 
is gradually giving way, and that our great Universities 
are at last becoming alive to the importance of this branch 
of learning, and to the necessity for encouraging its pur- 
suit among the students. It is a matter for surprise that 
no similar mention of rewards for Natural Science is 
ever made with respect to the University of Dublin. 
And yet, were a Fellow of Trinity Ccllege asked what 
was being done in this direction at his University ? he 
would probably answer, “ Oh, a great deal! there are gold 
and silver medals awarded at the Moderatorship Examina- 
tion for Natural and Experimental Science ; then there 
are four or five Science Scholarships given annually.” It 
is true a student may take out his degree with honours in 
Natural Science, and receives a medal, but let us see 
what is the course for the so-called Science Scholarships ; 
the subjects are mathematics, pure and applied, for which 
350 marks are obtainable, and, as a secondary course, 
either logic or physics, for which fifty marks alone are 
given. Such are the rewards and inducements held out 
to the student of Natural Science. It ‘s scarcely to be 
wondered at that the most promising men in the University 
do not go in for them, but devote themselves to the more 
profitable classics or mathematics. For these the rewards 
are liberal and numerous; there are no less than seventy 
foundation scho'arships, and many others, besides a great 
number of exhibitions, of which, within the last few 
months, thirty in addition have been granted by the 
Board. Not one of these has the man who devotes him- 
self to chemistry, zoology, botany—in short, to Natural 
Science—a chance cf obtaining. We ask—is this fair? 
Even supposing it unadvisable to divert any of these 
scholarships or exhibitions from their accustomed chan- 
nels, yet surely the Board might establish one or two 
additional ones out of the—confessed to—6o,o0co/. annual 
income. 
About a year ago it was ‘rumoured that a “student- 
ship” would in future be given at the degree examination 

NATURE 


(Dec 15, 1870 

to the first gold medallist in Natural Science, but the idea 
seems to have died a natural death, and those in whose 
bosoms a ray of hope had arisen have been doomed to 
disappointment. It is not to be supposed that the authori- 
ties of Trinity College, Dublin, are in any great degree 
adverse to changes. On the contrary, when a reform (?) 
is not especially needed, they are not unlikely to introduce 
it ; thus, for instance, the harmless old custom of setting 
the college clock a quarter of an hour late—giving the 
students, as it were, a quarter of an hour's law—has been 
abolished, and the hour for “commons” has been altered. 
But we have no wish to lead any one to imagine that 
an altogether bigoted and unchanging spirit pervades the 
University : we have much pleasure in saying that many 
of its institutions are truly liberal ; and we can scarcely 
doubt that before long the governing body will look with 
more favour on the Natural Sciences, and that they will 
become aware that Ireland—not so very flourishing at 
present—will be anything but a loser when the National 
University sends forth a greaternumber of scientific men. 

THE CONSTRUCTION OF HEAVY ARTILLERY 
ii: 
CHOICE OF MATERIAL 
_ an article which appeared on the 24th of last month, 
we endeavoured to explain the construction of our 
large ordnance, and to trace briefly the steps by which 
the combined strength and simplicity of the present 
pattern in the British service—the Woolwich Gun, as in- 
vented by Mr, Fraser—were attained. Simplicity is one 
chief element of strength; the fewer pieces anything is 
made of in general the stronger it is, and it has also the 
advantage of cheapness; but simplicity is seldom the 
beginning, it is rather the end of a series of inventions 
and improvements, and this has been the case in gun 
manufacture. 
Having traced the steps of the process, and glanced at 
the history of its development, one topic more remains to 
be treated in order to give completeness to the subject, 
and that is the choice of material ; and although the choice 
of material must come first in actual construction, to know 
the manner in which the gun is formed, and the qualities 
sought to be developed in the construction, will be a great 
help in understanding what qualities it is desirable that the 
material should possess. There are two qualities between 
which the choice lies ; these are hardness and toughness. 
The British Government has decided, we think wisely, in 
favour of the latter. Hardness is the proper quality to 
resist a statical force, or pressure; toughness to resist a 
dynamical force or blow, and the explosion of gunpowder 
is not only a dynamical force, but it is the greatest that we 
have to deal with in any mechanical preblems. If a hard 
substance is subjected only to a blow which it is quite 
able to resist, whose strain is well within the limits of its 
elasticity, then it is a very fit and proper material for the 
purpose ; and this was the case with the old smooth-bore 
guns, which were all cast-iron. They were quite strong 
enough to do with safety all that was required of them. 
But for the force now imparted to rifled projectiles with 
their immense range, their tremendous armour-piercing 
vis viva, cast-iron guns are altogether inadequate. 
Much lower charges than those ot our wrought-iron 
rifled guns would burst them into fragments. Did 
nature supply us with a material so hard that the 
strain of gunpowder was easily overcome by it, it 
would do very well for all guns. If, for instance, diamonds 
existed of sufficient size that a piece of heavy artillery 
might be bored from one, then they would be a very 
admirable material for the purpese. but, as this is not the 
case, we must fall back on tough instead of hard sub- 
stances, the more especially as it does not do to approach 
