22 AN ACCOUNT OF THE EARLY MATHEMATICAL AND 



" why a light body floating in a tea cup, or other vessel, when 

 approaching the side, moves towards it with a rapidly accele- 

 rated motion," is next explained by him to exist in "the 

 universal attraction of matter," since an effect similar to this 

 is that by which a plummet is drawn from the perpendicular 

 by the attraction of a hill. His own inquiry why " after 

 having been exposed for some time to a very cold wind, a 

 person feels himself much benumbed, but soon after, on com- 

 ing under shelter, the cold is suddenly changed into as great 

 an extreme of heat," is accounted for by himself from the 

 fact that " the internal principle producing" the constant 

 heat of the blood, " whatever it may be, must perpetually 

 vary in its effect, so as to counterbalance the opposite in- 

 fluence of the external air on the body, be it greater or less." 

 Such being the case, cold must excite this principle to greater 

 activity, and hence the extreme heat experienced under the 

 circumstances of the query. The fourth query, Mr. Dalton 

 observes, " points out its own answer. Metals being the 

 best conductors of heat will cool fastest, and consequently the 

 heat so communicated to the metal scale by the thermometer 

 will be dispersed faster than that communicated to the ivory 

 one, which consequently delays the ascent a little; — in the 

 same manner as a vessel would be longer in filling with water 

 when there was an aperture in the bottom of one inch diame- 

 ter, than when the aperture was only half an inch diameter." 



In the mathematical department his solution to question 

 951 is the only one printed at length. It was proposed by 

 Mr. George Sanderson, of London, and requires " to deter- 

 mine on which day of the year 1792^ the time between noon 

 and sunset will be the greatest possible at Petersburgh in lat. 

 59° 56' north." Mr. Dalton's investigation affords an in- 

 teresting specimen of the use of the equation of time, and on 

 this account appears well worthy of being transcribed. 



Question ^b\. Answered by Mr, John Dalton, " By the 

 word noon, in this question, I suppose is meant 12 o'clock, 



