46 --  RepORT—I1858. 
Tt has been known for a long time that water acts more or less upon glass, slowly 
decomposing it. Scheele, for example, observed that distilled water, which had been 
boiled a long time in glass vessels, became alkaline. Ebelmen published some time 
ago an account of the strong action of water charged with carbonic acid on glass. 
Mr. H. C. Sorby had lately shown the author some specimens of glass which had 
rapidly undergone partial devitrification during their exposure to the action of water 
boiling under pressure, at a temperature exceeding 300° C. The action of water on 
glass is materially assisted by the presence of ammonia. Glass in stable windows is 
frequently corroded from this cause. The disintegration of the glass found in the lake 
at Walton Hall appeared to the author to have arisen from the combined action of 
the water and the ammoniacal and carbonic acid gases derived from the mud, assisted 
by the pressure resulting from the superincumbent water. It is probable that the 
transformation of the glass was produced by the silica of the glass, after the separation 
of the alkali, being left in a gelatinous state, entering into combination with lime, 
derived from the mud or water of the lake, to form the insoluble silicate of which the 
scales were composed, analogous in composition to tabular spar. 
The author next proceeded to a consideration of the peculiar colour of the glass. 
On fusing the glass, after removing the scales, it was perfectly colourless. The de- 
tached scales, which were very difficult to fuse, likewise became colourless. The 
coloured glass, viewed by transmitted light, exhibited rays of colour complementary 
to the reflected rays. ‘The various colours presented, therefore, doubtless owed their 
origin to the different refractive powers of each of the scales; the refractive powers 
of the latter again depending on their thickness. 
On the Expansion of Metals, Alloys, and Salts. 
By F. Crace Carvert, £.C.S8. 
Messrs. Calvert and R. Johnson having purified a considerable number of metal 
for the purpose of ascertaining some of their properties, were desirous of testing their 
expansion and contraction when exposed to certain temperatures, ‘The apparatus 
employed in making these experiments is one constructed by Mr. G. C. Lowe. It 
consists of a lever with a long and a short arm. The short arm is brought to bear 
upon the bar to be tested, and in the end of the long arm the object-glass of a tele- 
scope is inserted. An eyepiece of considerable magnifying power is so fixed, that an 
observer, by looking through it, at a graduated scale, is able to determine with the 
greatest accuracy the distances through which the object-glass is displaced when heat 
is applied to the bar. The parts of the apparatus are so adjusted that sromodth part 
of an inch expansion is represented by a definite portion of the graduated scale. 
In the course of these experiments it was found that marked differences were ob- 
served between the results obtained and those of previous experimenters. This was 
attributed to the circumstance of the metals they were employing being in a pure 
state, and this view was confirmed by trying in the same manner metals of ordinary 
commercial quality. They observed also that a change of the molecular condition of 
a bar produced a considerable change in its ratio of expansion. Thus a bar of steel, 
when tempered to an extreme hardness, has a ratio of expansion fully one-third greater 
than when it is left soft from the fire ; and most of the metals have a very different 
ratio according as they are cast or forged. This is particularly remarkable in the case 
of pure zinc, a bar of which, when well-hammered, expands very little more than half 
the amount that it expands when cast vertically. Again, the axis of crystallization has 
a considerable influence upon the expansion of bodies. A bar of pure zine cast hori- 
zontally expands much less than if cast vertically. A similar phenomenon was ob- 
served also in examining other crystalline bodies. ‘hus amongst the carbonates of 
lime, statuary marble was observed to expand more than some of the metals, amongst 
which are cast iron, antimony, and platinum ; whilst the expansion of chalk, in which 
the particles are differently arranged, is little more than one-fourth that of marble. In 
several alloys of metals a remarkable difference was observed between the expansion 
found by experiment and that calculated from by the ratios of the metals of which 
they were composed. Four different alloys were made and examined, and in each 
the expansion observed was less than that deduced by calculation from their equiva- 
