On the Lumincmsness of the Ocean. 3S1 



lowering, cloudy, and much overcast. Cold and heat seem to have 

 little influence upon this phenomenon ; for, on the Bank of New- 

 foundland, the phosphorescence is often very strong at the se- 

 verest time of the winter. Sometimes, all other circumstances 

 appearing to be the same, the phosphorescence is very distinct 

 on one night, and the following night there is scarcely any. 

 Does the atmosphere favour this disengagement of light, this 

 combustion of phosphuretted hydrogen ? Or do not these dif- 

 ferences depend merely upon chance, which leads the navigator 

 into a sea more or less filled with mollusca ? Perhaps, also, the 

 luminous animals only come to the surface of the sea when the 

 atmosphere is in a certain state. M. Bory St. Vincent, asks 

 with reason, why our fresh marsh-water, which is filled with po- 

 lypi, is not luminous ? It would appear in fact, that a particu- 

 lar mixture of organic particles is necessary to favour this dis- 

 engagement of light. Willow-wood is more phosphorescent 

 than oak. In England, salt-water has been rendered luminous 

 by casting herring brine into it. Galvanic experiments shew 

 that the luminous state of living animals depends upon an irri- 

 tation of the nerves. I have seen an Elater noctilucus, which 

 died, diffuse a strong glow when I touched its anterior extremi* 

 ties with tin or silver. Sometimes, also, the medusae give out a 

 stronger light at the moment when the galvanic chain is closed. 

 Humboldt, Tableaux de la Nature, torn. ii. p. 80-87. 



Observations on the Structure nf Feathers and Hair. 



I. Observations on ike Structure and Development of Feathers ; by 

 Fred. Cuvier. (Mem. du Museum d'Hist. Nat. t. xiii. 

 p. 327.) — Inquiries into the Structure and Development of 

 the Prickles of the Porcupine, followed by Observations on 

 Hair in general, and on its Zoological Characters ; by the 

 same. (Read to the Academie des Sciences, Oct. 1827.) 



IN the first of these Essays M. F. Cuvier explained the struc- 

 ture and development of feathers; and imagined that he bad 

 discovered differences between their development and that of 

 hairs, which had been considered as analogous ; but in the se- 

 cond he has compared and united the modes of formation of 



