332 On the Quantity of Carbonic Acid Gas [Nov. 



was in an highly electrical state. What is singular, a friend 

 who spent the evening with me, and who at my desire made the 

 experiment about 10 p. m., was found to emit about 4*90 per 

 cent., whereas since that time we have once or twice repeated 

 the experiment at about the same hour, and found it only 4*10 

 or 4'20 per cent., which appears to be his usual minimum. 

 Hence it would seem that the circumstance was not peculiar to 

 myself. 



Two days after this remarkable increase, there occurred a no 

 less remarkable decrease, or depression below the usual standard. 

 The maximum took place earlier than ever I had seen it, that is, 

 at 10 h 30' a. m., and was also less, amounting only to 3*70 per 

 cent. The minimum also took place earlier, and was greater 

 than usual,* that is, at 7 h 45' p. m., it was 3-40 per cent, where 

 it continued the whole evening. During this period the baro- 

 meter was about 30*20, the thermometer 60, and, as in the 

 former instance, I was not aware of any circumstance whatever 

 to which I could refer it. The following day was also generally 

 below the standard, though not in the same remarkable degree. 

 In the annexed diagram 1 have drawn these extremes of variation 

 along with the mean, in order that they might be rendered more 

 conspicuous by the contrast. See Plate XII. : where the upper 

 line represents the greatest deviation above the mean observed j 

 the lower line, the least deviation. 



Besides these, there are some minor variations, which may be 

 here mentioned. One of them is a slight depression occasionally 

 between 6 and 8 a. m., which I have attributed to a less active 

 state of the system, on account of abstinence, f This is very 

 trifling, amounting only to 0*2 or 0*3 per cent., and sometimes 

 is not at all perceptible. Another is, an extraordinary diminu- 

 tion of short continuance, immediately after the maximum, 

 sometimes even below the usual minimum itself. This I have 

 observed only when the maximum has been greater, and more 

 abrupt in its ascent, than usual. It may, I presume, be accounted 

 for on a principle of the second law to be hereafter mentioned. 

 One example of this variation we have in the extraordinary 

 instance of great increase above described. When the increase 

 has been gradual, the decrease has been constantly the same. 



2dly. The quantity of oxygen gas consumed, and conse- 

 quently of carbonic acid gas formed, in a given time, is cer- 

 tainly very different in different individuals. Future investiga- 

 tions, however, must decide this important question, more 



• I have generally found that when the maximum has been less than usual, 

 the minimum has been greater in proportion : i. e. at least equal to the usual 

 standard of 3 - 30 per cent., and sometimes above it. I have never seen the 

 minimum permanently lower than 3 - 30 per cent. 



+ Perhaps, however, it may be accounted for on another principle. See 

 Illustration of Law II. 



