I90 OBSERVATIONS ON THE GANNET, 



in all seasons, without attempting to near the 

 shore. 



This contrivance may also be of the most im- 

 portant service to an animal which is constantly ex- 

 posed, even in the most inclement season, and cannot 

 quit its station without starving : nothing could 

 possibly conduce more to its security against in- 

 tense cold, or be better adapted to preserve the 

 necessary temperature of animal-heat, than this 

 intermediate body of air between the skin and the 

 body, since that element is found to-be a non- 

 conductor of heat. Upon this principle, what 

 animal can be more securely protected against 

 cold, ©r retain its vital heat so effectually as the 

 gannet, or such birds as are almost surrounded 

 with a body of confined air, divided by cells, and 

 intersected by membranes between the skin and 

 the body, and that skin so amply covered with a 

 light porous substance, filled also with air, and 

 impervious to water # ? 



* The Gannet is capable of containing about three 

 full inspirations of my lungs, divided into nearly three 

 equal portions, the cellular parts under the skin, on each 

 side, holding nearly as much as the cavity of the body. 

 Now, as a full or extraordinary expiration of the human 

 lungs has been considered to occupy a space of about 

 sixty cubic inches, (Phil. Trans, vol. 69. p. 349«)> so 

 the gannet is capable of containing not less than 180 

 cubic inches of air at one time, subject to the will of the 

 bird, under certain impressions. 



