186 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



tire results of these researches, therefore, sustain the previ- 

 sion of theory in making the carbon and the silicon atom 

 chemically identical in combining power, each being equal 

 to four hydrogen atoms. The question which still remains 

 to be solved is whether that property, at present peculiar to 

 carbon, by which it is able to combine with itself, and thus 

 to form a nucleus containing from two to thirty carbon atoms 

 a property which more than any other so admirably fits it 

 for its uses in organic nature is possessed by silicon. At 

 present no group of more than two similar atoms united to 

 each other is known to exist in any compound with which 

 chemistry is acquainted, if the groups which carbon forms be 

 excepted. 1 A, 1873, 237. 



THE CHEMICAL FOKCE OF THE SOLAR RAYS. 



The chemical force in the rays of the sun has been studied 

 from a new point of view by Marchand, who has communi- 

 cated numerous interesting results to the Paris Academy of 

 Sciences. Marchand's method differs from that adopted by 

 Bunsen and Roscoe in that he measures the effect of the sun- 

 light on a solution of perchloride of iron and of oxalic acid, 

 and not on a mixture of chloride and l)vdro2;en. He esti- 

 mates the chemical effect as one quite independent of the 

 heatino* effect, but does not seem to have arrived at the ad- 

 vanced views indicated by the studies of Professor Draper, 

 of New York, in whose opinion the solar rays are not a com- 

 plicated mixture of caloric, luminous, and actinic rays, but a 

 simple phenomenon whose results are tripartite, according to 

 the nature of the body on which they act. Marchand has 

 for four years continued the daily use of his photometric liq- 

 uid, and submits conclusions interesting to both chemists and 

 physicists. He finds that his liquid is acted on specially 

 by the rays between Fraunhofer's F and G lines; he gives 

 the law according to which the thickness of the atmosphere 

 diminishes the effect of the sun in decomposing the liquid 

 and liberatimr carbonic acid o-as: he finds that the chemical- 

 ly active rays are not affected by atmospheric currents, and 

 therefore the chemical climate is a different one from the 

 trhermal climate. The total daily photochemical force is, ac- 

 cording to Marchand, greater at the pole than at the equator 

 at the time of the solstice. The earth's atmosphere, in so 



