1813.] emitted from the Litngs during Respiration. 331 



Having spoken of the law as it obtains generally, we come 

 now to consider its variations : these may be classed under the 

 two following heads : — 



1. Variations in the quantity of carbonic acid gas, as given off 

 by the same individual on different days. 



2. Variations in its quantity, as given off by different indivi- 

 duals. 



The first of these variations I have observed in a greater or 

 less degree, several times ; indeed, no two days are exactly alike. 

 But by far the most remarkable day that has come under my 

 observation was the 22d of August, the maximum of which, 

 exactly at noon, was as high as 4-90 per cent., and the mini- 

 mum, at S 11 20' p.m., as high as 4" 15 percent. I had been up 

 all the preceding night, for the first time; and hence was 

 inclined, though contrary to my judgment, to attribute it to that 

 circumstance ; but on this being repeated, no such event fol- 

 lowed, as I expected. What is remarkable, it had evidently 

 begun to rise on the evening of the 21st ; for at 9 h liG' p. m. of 

 that day, I found the quantity as high as 3*50 per cent., at ieast 

 0*2 per cent, higher than the usual minimum. From this point 

 it continued to increase gradually till day-break, or a little before 

 3 a. m., when it suddenly rose up to 390 per cent. At 9 h 50' 

 a. m. it was 4'00 per cent. At 10 h 25' a. m. 4*40 per cent., 

 where it continued till alter 11 a. m., when it suddenly rose up 

 to 4'90 per cent., as before mentioned. From this point, how- 

 ever, it sunk rapidly ; so that at 12' 1 30' p. m. it was only 4-30 

 per cent., and afterwards, at 2 h 30' p. m., as low as 3-90 per 

 cent., from whence it rose, apparently gradually, to 44 5 per 

 cent., where, as before stated, it was at 8 h 20' p. m. When 

 this remarkable period ended 1 do not know ; but the next day 

 it was very little, if at all, above the usual standard, it is proper 

 to observe, that during (his period 1 was not aware of the least 

 difference whatever in my health, or any other circumstance that 

 could enable me to account for it. 1 fancied my respiration was 

 more tree, and that I felt lighter than usual ; and this might be 

 the case; but these were so trifling that 1 am confident they 

 would have escaped my notice had it not been particularly 

 directed to the subject. The barometer varied from 29-80 to 

 29*70 during the day. which was rather below* the mean .of 

 the preceding and subsequent periods. The mean of the ther- 

 mometer's range was <>i. The hygrometer made considerable 

 advances during the day towards damp : the air was calm, and 

 show isioi ally fill composed of very large drops, as occurs 



in thunder weather: in the evening there was, a good deal of 

 lain. 1 have reason to believe, therefore, that the atmosphere 



• Gfepmllj ■peaking, I think I have found the quantity incTcn.se during the 

 linking of the Ij..iuli. ler, 



