1869.] Chemical Science. 593 



Dr. Tyndall, were of glass, with flat glass ends, and glass stop- 

 cocks. After exhausting the air from the tube, he permitted a 

 mixture of absolutely pure dry hydrogen and nitrogen gas to enter, 

 and on passing a cone of sunlight from a lens through the long axis 

 of the tube, he was surprised to see a cloud formmg, because of 

 chemical decomposition set up. This led him to question the 

 method employed to dry the gases, which was by passing them 

 through powdered glass wetted with sulphuric acid. When chlo- 

 ride of calcium and other methods of drying gases were tried, no 

 clouds were formed by the sunlight, so at last he came to the con- 

 clusion that a source of error lay in a trace of sulphurous acid gas, 

 taken up by the hydrogen and the nitrogen from the sulphuric acid. 

 The latter acid employed by him was absolutely pure, and con- 

 tained no trace of arsenic from the use of impure sulphur in its 

 manufacture. In the remainder of his paper he explained the 

 exact nature of the chemical reactions which took place in his tube, 

 which reactions he, like Dr. Tyndall, ascribed to a motion of sepa- 

 ration set up between the atoms of each molecule, by the short blue 

 and violet waves of the solar spectrum. 



Mr. W. Huggins, F.E.S., read a paper " On the Heat of the 

 Stars." The instruments used were a telescope, a very sensitive 

 thermopile, and a galvanometer, by means of which faint indications 

 of heat were obtained, accompanying the light from different stars. 



Dr. Balfour Stewart F.E.S., read a paper on a very cleverly 

 designed " New Kain Gauge," invented, made, and tested by Mr. 

 Beckley, of Kew Observatory. 



Chemical Science. (Section B.) 



The proceedings in this Section were opened by an address by 

 the President, Dr. Debus, in which he reviewed the various di- 

 rections in which chemical science was progressing, and directed 

 attention to some of the fundamental ideas which guide chemists in 

 then- researches. The address was hstened to with great attention, 

 but is too technical to admit of more than this brief allusion to it. 

 Most of the j)apers and reports communicated to this Section were 

 on subjects of special more than general interest, and will not bear 

 condensation. We will therefore select a few only of the papers 

 which treat upon matters likely to be of general interest to our 

 readers. 



Dr. Jacobi read a paper on the "Electro Deposit of Iron," 

 illustrating his remarks by a series of plates of extreme beauty. 

 The solution from which the metallic iron was deposited consisted 

 of a double sulphate of iron and magnesia. It was found desirable 



VOL. VI. 2 s 



