80 FRAGMENTS OF SCIENCE. 



The remark already made, as to the bearing of the 

 decomposition of nitrite of amyl by light on the question 

 of molecular absorption, applies here also; for were the 

 absorption the work of the molecule as a whole, the iodine 

 would not be dislodged from the allyl with which it is 

 combined. The non-synchronism of iodine with the 

 waves of obscure heat is illustrated by its marvelous trans- 

 parency to such heat. May not its synchronism with the 

 waves of light in the present instance be the cause of its 

 divorce from the allyl? 



Iodide of Isopropyl. The action of light upon the vapor 

 of this liquid is, at first, more languid than upon iodide of 

 allyl; indeed many beautiful reactions may be overlooked, 

 in consequence of this languor at the commencement. 

 After some minutes' exposure, however, clouds begin to 

 form, which grow in density and in beauty as the light 

 continues to act. In every experiment hitherto made 

 with this substance the column of cloud filling the experi- 

 mental tube was divided into two distinct parts near the 

 middle of the tube. In one experiment a globe of cloud 

 formed at the center, from which, right and left, issued 

 an axis uniting the globe with two adjacent cylinders. 

 Both globe and cylinders were animated by a common 

 motion of rotation. As the action continued, paroxysms 

 of motion were manifested; the various parts of the cloud 

 would rush through each other with sudden violence. 

 During these motions beautiful and grotesque cloud-forms 

 were developed. At some places the nebulous mass would 

 become ribbed so as to resemble the graining of wood; a 

 longitudinal motion would at times generate in it a series 

 of curved transverse bands, the retarding influence of the 

 sides of the tube causing an appearance resembling, on a 

 small scale, the dirt-bands of the Mer de Glace. In the 

 anterior portion of the tube those sudden commotions 

 were most intense; here buds of cloud would sprout forth, 

 and grow in a few seconds into perfect flower-like forms. 

 The cloud of iodide of isopropyl had a character of its own, 

 and differed materially from all others that* I had seen. A 

 gorgeous mauve color was observed in the last twelve inches 

 of the tube; the vapor of iodine was present and it may 

 have been the sky- blue scattered by the precipitated par- 

 ticles which, mingling with the purple of the iodine, pro- 

 duced the. mauve, As in all other cases here adduced, the. 



