1865.] Dr. Davy on the Temperature %c. of Birds. 337 



vanish, the quantities b, c remain stationary in the above double infinite series; 

 in the two other cases, the b quantities and c quantities continually increase 

 in one direction and continually decrease in the other, the increase taking 

 place in that direction in which we must read the successions of sign of 

 the derivatives of F so as to begin with passing from plus to minus. 



(4) To the increase of b and c there is no limit, but to the decrease of 



each there is a limit, viz. a? d 3 and a 3 d? are the limits towards which the 

 b and the c terms respectively converge. 



I conclude with remarking that the above theorem is only a particular 

 illustration, and the most simple that can be given, of a very wide theory 

 relating to discriminants of all orders which springs as an immediate con- 

 sequence from the principles involved in the theory of variation of algebra- 

 ical forms referred to in the note which I had recently the honour of laying 

 before the Society. 



VI. " Some Observations on Birds, chiefly in relation to their Tem- 

 perature, with Supplementary Additions." By JOHN DAVY, M.D. 

 F.R.S., &c. Eeceived May 26, 1865. 



(Abstract.) 



This paper consists of four parts : 



In part first the author gives the results of his observations on the tem- 

 perature of the common fowl (as many as sixty-two), made at different seasons 

 of the year, showing that the temperature of this bird ranges from 107 to 

 109Fahr. in recto; that that of the male is a little higher than that of 

 the female, and of both, higher in summer than in winter. 



He states that he was induced to pay so much attention to the tempera- 

 ture of the common fowl, from Mr. Hunter having assigned it a temperature 

 no higher than between 1 03 and 1 04, a degree reached by some of the 

 mammalia, and even exceeded. 



The second part contains the results of the author's experiments on the air 

 expired by a certain number of birds, and on the air contained in their air- 

 receptacles and bones. They are introduced with some observations on the 

 length of time birds are capable of retaining life under water, from which it 

 appears that it differs greatly in different species, varying from ten minutes, 

 as in the instance of the duck, to half a minute, as in the instance of the 

 owl. 



From the analysis of the air expired in the act of drowning, it would ap- 

 pear that there is a certain loss of carbonic acid, equivalent to the propor- 

 tion of oxygen less than exists in the atmospheric air expired, a loss, it is 

 inferred, owing to absorption by the blood of the gas which has disappeared, 

 as indeed is indicated by the darkness of colour of this fluid, and confirmed 

 by the effects of exhaustion by the air-pump. 



A deficiency, too, of carbonic acid was found in the air of the air-recep- 



