1867.] Physical Science. 563 



Prof. J. Clerk Maxwell read a paper on a real image stereoscope. 

 In this instrument a frame containing a large single lens is placed 

 in front of the pictures, and the observer stands about two feet from 

 the instrument ; he then sees, just in front of the lens, a real and 

 inverted image of each of the two pictures, the union of which 

 forms the appearance of a solid figure in the air between himself 

 and the apparatus. 



Dr. Balfour Stewart, Superintendent of Kew Observatory, read 

 a paper " On the Behaviour of the Aneroid Barometer at different 

 Pressures." Experiments had lately been made with the view of 

 ascertaining to what extent an Aneroid may be considered a reliable 

 instrument when exposed to considerable changes of pressure, such 

 as occur in mountain districts. By means of an air-pump, the 

 Aneroids, whon placed in a receiver, might be subjected to any 

 pressure. A method of tapping the Aneroids had also been devised, 

 and by this means the experiments as to the deviation of the results 

 given by these instruments were conducted with comparative ease, 

 and with the greatest accuracy. 



The next day Mr. Grlaisher gave a report on luminous meteors, 

 which was followed by an interesting discussion in which Pro- 

 fessor A. Herschel said that the connection between comets and 

 meteors had this year been established without doubt. He would 

 not say that every shooting star was a comet. They were more 

 likely the dissipated parte of comets — probably comets torn into 

 shreds by the sun's attraction drawing them into space. 



Some papers by Sir David Brewster on various optical subjects 

 followed : one of these gave an account of experiments which, Sir 

 David remarked, were sufficient to establish the almost incredible 

 truth, that the colours of the soap bubble are not produced by 

 different thicknesses of the film itself, but by the secretion from it 

 of a new substance flowing over the film, expanding under the 

 influence of gravity and molecular forces into coloured groups of 

 various shapes, and returning spontaneously, when not returned 

 forcibly, into the parent film. 



The President, Sir William Thomson, next read an important 

 paper on a new electrical machine founded on induction and 

 convection. The principle of the machine was that of the 

 " Successful Merchant," who commenced his life with the capital of 

 ^d., and after a month's persevering industry, realized the handsome 

 sum of £1, and continued to go on increasing his capital at a 

 compound rate of interest. The object of the instrument referred 

 to was not indeed to increase money, but electricity, and that 

 increase was at a compound rate. Precisely in conformity to the 

 law which applied to compound interest and the increase of the 



