324 Proceedings of the British Association. 



the observer, of vapor or water in a vesicular state. Col. Reid's 

 letter also contains the following statement : " Three days ago 

 (i. e. Aug. 14, 1839) T 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, I 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 decomposed in 

 films of considerable irregularity, their surfaces having a finely 

 mammillated appearance convex on one side and concave 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 indeed, 

 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 on the 

 leading rays of the thermonietric spectrum. In the decomposed 



