66 Mr Dalton on the QuantHij of Food 



acquired, I varied the process, with a view to obtain the quantity 

 of perspiration, and the circumstances attending it more directly. 

 I procured a weighing beam, by which I could weigh my own 

 body, so that the beam would turn with one ounce. Dividing 

 the day into periods of four hours in the forenoon, four or five 

 hours in the afternoon, and nine in the night ; or from ten o'clock 

 at night to seven in the morning. I endeavoured to find the 

 perspiration corresponding to those periods respectively. 



My method of proceeding was, to weigh myself directly after 

 breakfast, and again before dinner, observing neither to take or 

 part with any thing during the interim, besides what was lost by 

 hisensible perspiration; the difference in the weights, in this case, 

 was the loss by perspiration. The same procedure was adopted 

 in the afternoon and in the night. 



I continued this train of experiments for three weeks in No- 

 vember, the same year. I then took the aggregate of the mor- 

 ning observations, next that of the afternoon observations, and 

 lastly, that of the night observations, and divided each of those 

 three aggregates by the number of hours in the several periods, 

 in order to find the hourly perspiration in each period, appre- 

 hending that there might be some differences owing to the time 

 of the day, or being awake or in sleep. 



The mean hourly losses by perspiration, were as under : 



Morning, 1.8 ounce avoirdupois. 



Afternoon, 1.67 



Night, 1.5 



During twelve days of this period, I kept an account of urine, 

 corresponding in time with that of perspiration. The ratio was 

 urine : perspiration 46 : 33, or 7 to 5 nearly ; which is somewhat 

 greater disproportion than that observed in March ; owing pro- 

 bablv to the temperature of the weather being lower in the lat- 

 ter season. 



So far I have given the facts and observations made forty 

 years since ; I made no deductions from them at the time ; in- 

 deed, the knowledge of animal and vegetable chemistry was at 

 that time in its infancy. Since then, the progress of this branch 

 of philosophy has been very considerable, and we are now en- 

 abled to approximate, in a good degree, to the quantities of the 



