196 On the Influence of Solar Light on Combustion. 



Prom the foregoing discussion it is evident that the subject 

 demands a thorough experimental investigation, with a minute 

 attention to all the external conditions which may influence the 

 results. This I propose to undertake during the next twelve 

 months. In the meantime it is hoped that these preliminary 

 researches may prepare the way for a clearer appreciation of the 

 difficulties which are to be encountered. Pei'haps, however, in 

 the present stage we may be warranted in deducing two conclu- 



M. Vierordt tested the effects of barometric pressm-e between 29-309 and 

 30-197 inches. The average rise of 0-5036 of an inch 



Increased the air expired 35-/46 cubic inches per minute. 



„ number of respirations 0-/4 „ „ 



„ „ pulse 1-30 „ „ 



Dr. Hutchinson found that in a mine 1488 feet deep, where the pressure 

 was 1-54 inch more than at the sea-level, the respiration was increased 2-4 

 ]>er minute, and the pulse 1-3 per minute. {Cyc.of Anat. et Physiol, [art. 

 Respiration], vol. iv. pp. 348, 349. Lond. 1852.) 



Analogous effects are produced bj' temperature. In the famous experi- 

 ments of Scguin and Lavoisier, at 82° F., the former (fasting aud at rest) 

 consumed 1210 French cubic inches of oxygen per hour; whereas at 57°, 

 he consumed 1344 cubic inches per hour. {Memoires de l' Acad. Royaleiov 

 1789.) Dr. Crawford found that a guinea-pig at 55°-5 F. abstracted twice 

 as much oxvgen from the aii- as at 104° F. (Experiments and Observations 

 on Animal Heat, 2ud edit. p. 311-315. Lond. 1788.) Dr. W. F. Edwards 

 found that birds consume more oxygen in winter than in summer. (De 

 rinfluence des Agens Physiques sur la Vie, chap. 6. p. 195. Paris, 1824.) 

 The best experiments are those of M. Vierordt. {Op. cit. supra.) He ob- 

 tained the following results between 37°"4 and 75°'2 F. : — 



M. Felix Letellier's experiments on warm-blooded animals confirm these 

 results. He found the amount of carbonic acid evolved per hour at differ- 

 ent temperatures to be as follows : — 



(Vide Comptes Rendus, vol. xx. p. 795. Paris, 1845. Also Ann. de Chim. 

 et de Phys. 3rd series, vol. xiii. p. 478. Paris, 1845.) Doubtless physio- 

 logical reactions exercise a powerful influence over the results of such ex- 

 periments ; nevertheless, as respiration is essentially a process of combus- 

 tion, they have a general bearing on the question under consideration. 



