124 CJironicles uf Science. [Jan., 



IX. PHYSICS. 



Light. — We have very few facts to chronicle this quarter in Physical 

 Science. One of the most valuable contributions to our knowledge of 

 the phenomena of Light has been made by Mr. Dibbitts,* who, in a 

 paper on the Spectra of the Flames of various Gases has recorded obser- 

 vations made on the flame of hydrogen burnt in air, in oxygen, in 

 nitrous and nitric oxide, and in chlorine ; also of carbonic oxide and 

 cyanogen, burnt in air, oxygen and nitrous oxide. The flames of am- 

 monia, sulphuretted hydrogen, and of some other gases have been also 

 examined under various conditions, the whole forming a most valuable 

 contribution to our knowledge of the subject. A curious fact dis- 

 covered by the author is, that a solution of sulphate of quinine does 

 not fluoresce with the light of the flame from hydrogen, hydrocarbons, 

 and ammonia, but does with the flame of carbonic oxide, cyanogen, 

 sulphur, and indeed all sulphur compounds. When fluorescence does 

 take place, it is always stronger with the flame in oxygen. 



It is well known that Santonine is coloured yellow by exposure to 

 solar light, and this takes place in a vacuum as well as in air. It does 

 not take place, however, when the actinic rays are cut off by means of 

 a solution of nitrate of uranium. This phenomenon has been examined 

 by M. Sestini,f who finds that Santonine when exposed to solar light 

 is changed into formic acid, and an uncrystallizable substance much 

 more soluble in alcohol and ether than santonine itself, and also a rod 

 resinous substance. To the yellow uncrystallizable substance the 

 author has given the name of photo-santonic acid. 



Some living specimens of the Gucuyos, or fire-flies (Elater noctilucus), 

 coleopterous insects, very common in Mexico, have lately been brought 

 to Paris, where they have created quite a furore, not only amongst the 

 Parisian belles, who are anxious to put them to the same use as the 

 Mexican ladies, but also amongst scientific men. They were exhibited 

 at the Academy of Sciences, at their sitting on the 19th of September, 

 where M. Pasteur read a paper on the properties of their phosphores- 

 cent light. The light emitted by these insects is so intense that one 

 will enable a person to read in the dark at a short distance from the 

 animal. Mexican ladies ornament themselves for evening parties with 

 the insects, keeping them for the purpose, feeding them on sugar, and 

 giving them a bath once or twice a day. The light examined by the 

 spectroscope gives merely a continuous spectrum, very beautiful, but 

 without lines. The author made the same observation with the light 

 of glowworms. As it seems possible to preserve these creatures for a 

 considerable length of time, and as Mexico is now in constant commu- 

 nication with Paris, some enterprising artificial florist will, no doubt, 

 import them regularly next season. 



Some valuable improvements in the production of light from gas 

 have recently been brought forward by the Rev. W. E. Bowditch.| 



* ' Poggendoiff s Annalen,' August, 1864. 



t 'Bulletin de la Societe Chimique de Paris,' 1864, p. 21. 



J 'Chemical News,' vol. x. pp, 192, 216. 



