598 MR J. Y. BUCHANAN ON THE COMPRESSIBILITY OF GLASS. 
We have then forthe apparent compressibility of water in glass’ at 2°5° C. 
48°68 per million per atmosphere. Adding 2°92 for the compressibility of 
glass, we have for the compressibility of water at 2°5° C. 51°60. Similarly at 
12:5° C. we have 45:39 for the apparent, and 48°31 for the real compressibility. 
GRASSI gives the following values for the true compressibility of water at 
various temperatures :—At 1°5° C.—51'5; at 41°—49°9; mean—50'7.. At 
10°8° C.—48°0; at 13°4°—47'7; mean—47'8. My results agree very closely 
with these. 
Before concluding, I would call attention to a very curious phenomenon, 
which I have never seen noticed, namely, the peculiar noise which accompanies 
the relief of pressure in a mixture of ice and water. In comparing the piezo- 
meter K, No. 4, in melting ice with the manometer at 12°5° C., I proceeded 
gradually from lower to higher pressures. When the pressure which was 
relieved was 100 or 120 atmospheres, I thought I noticed a slight noise. On 
raising the pressure higher the noise became more and more distinct, until 
when the pressure relieved was over 200 atmospheres, it was distinctly audible 
at a distance of five or six feet. It resembles the noise produced by bending 
a piece of tin backwards and forwards, and is markedly intensified by accele- 
rating the relief, just as the noise made by blowing off steam is intensified 
by enlarging the outlet. When the relief valve is opened very carefully it 
whispers gently but very distinctly, till the pressure is all down. If opened 
comparatively briskly, but still with great care, the noise is comparatively loud, 
but more rapidly used up. I forbear making any reflections until I have been 
able to study this phenomenon more closely. 
Pieces of clear ice which had been subjected to high pressure in the receiver 
were finely laminated in parallel planes. In each 
plane there was a central patch surrounded near 
the sides of the block by a ring of spherules. 
The annexed figure gives an idea of the arrange- 
ment. ‘The size of the spherules is greatly exag- 
gerated. 
The lamination of ice by pressure in one 
direction is well known. I am not aware that 
its production by pressure in all directions has 
been noticed. 
