fa 
ws - > * - 
: wt S 4° . 
324 Proceedings of the British Association. 
the observer, of vapor or water ina vesicular state. Col. Reid’s 
letter also contains the following statement: “Three days ago 
(i. e. Aug. 14, 1839) I had a fine opportunity of observing a wa- 
ter-spout under my house, and could with a spy-glass distinctly 
observe, that at the surface of the sea it was revolving like the 
hands of a watch, and the same observation was made at a tele- 
graph station near the government house. This is the fifth ac- 
count, well authenticated, in north latitude: all five revolved the 
same way.’ " 
On the decomposition of glass, by Sir D. Brewster.—There is 
no subject more curious or more instructive than the disintegra- 
tion of crystallized and uncrystallized bodies, either by the direct 
influence of chemical agents, or the slow process of natural de- 
composition. At the meeting at Edinburgh, | submitted, (said 
Sir D.) a brief account (since enlarged and published in the Edin-. 
burgh Transactions,) of remarkable optical phenomena produced 
by the instantaneous action of water and other fluids on crystals, 
and on their subsequent decomposition when placed in their sat- 
urated solutions. Since that time I have had occasion to examine 
the phenomena of decomposed glass, both of that which is found in 
Italy, and of specimens recently found in making excavations 
among the ruins of the Chapter-house of the Cathedral of St. An- 
drews. In decomposed glass, the decomposition commences in 
points, and extends itself either in planes so as to form thin films, 
or in concentric coats so as to form concentric films. When the 
centres of decomposition are near each other, the concentric films 
or strata which they form interfere with each other, or rather 
unite, and the effect of this is, that the glass is decompose 1 
films of considerable irregularity, their surfaces having a finely 
mammillated appearance convex on one side and concaye on the 
other. ‘The films thus formed, afford by transmitted light colors 
of infinite beauty and variety, surpassing any thing produced in 
works of art. They have the effect of dissecting, as it were, the 
compound surface of the solar prism, or of sifting and separating 
the superimposed colors, in a manner-analogous to what is produ- 
ced by colored and absorbing media. I have succeeded indee?, 
in producing one or more bands of white light incapable of de 
composition by the prism; and there can be no doubt that they 
will be found to exercise a similar or an analogous action oP the 
leading rays of the thermometric spectrum. In the decomposed 
ee 
