276 liemarks on Volcanoes. 



The memoir of Meyen is less extended, but it contains 

 some important facts.* The author admits three kinds of 

 phosphorescence ; 1. The phenomenon is owing to a mucosity 

 diffused in water. In that case, the water seen in the day 

 has a uniform tint of bluish-white. It is often observed in 

 tropical parts, but rarely out on the open sea. This mode 

 of phosphorescence may be produced artificially by washing 

 or by crushing certain molluscs and. acalephs either in sea- 

 water or in fresh ; 2. Phosphorescence results from the 

 presence of certain living animals, endowed with a luminous 

 mucus. This continues even after the death of the animal ; 

 it arises from a superficial oxydation of the mucous coating, 

 and it can be reproduced after it seems extinct by passing 

 the finger over the animal. The animals which owe their 

 luminous property to a secretion are, according to the author, 

 Infusoria, Rotifera, Biphorse, Medusae, Asteria, Cuttle fish, 

 Sertularise, Pennatuloe, Planarite, Crustacea, and Annelids : 

 3. The third cause of phosphorescence is in some animals 

 from the presence of one or more special organs. Of this 

 number are the Pyrosoma, and especially P. Atlantica, 

 whose light of a greenish blue is very brilliant. Each indi- 

 vidual carries behind its mouth a soft opaque substance of a 

 reddish brown colour. This body is slightly conical, and 

 under the microscope thirty or forty red points my be seen ; 

 it is this substance which produces the light. — {American 

 Journal of Science and Arts, vol. xv., No. 44, 2d Series, 

 p. 202. 



Dr Daubeny and Professor Bunsen of Heidelberg on 

 Volcanoes. 



Those who have taken the trouble of perusing my work 

 on Volcanoes, and especially the second edition of it, pub- 

 lished in 1848, will recollect, that in bringing forward that 

 theory which may be regarded as a revival, or perhaps a de- 

 velopment, of the original hypothesis of Sir Humphry Davy, 



* Beitraege zur Zoologie, von J. F. Meyen, fiinfte Abhandlung. Ueber das 

 Leuehten des Meeres. (Nov. Act. Nat. Ai\, t. xvi., Suppl., 1834.) 



