36 " Temperature of the Year. 



" For chemical decompositions, there is, perhaps, no battery 

 known so well adapted for them as the jars which I have describ- 

 ed. Their sustaining power is a great recommendation. The 

 extent of series will necessarily vary with the nature of the com- 

 pound operated on. We have found that a series of twelve jars 

 gives a sufficient intensity for the decomposition of acidulated wa- 

 ter, (water 10, sulphuric acid 1, or even much less.) Twenty- 

 four jars in a double series of twelve, give about twice as much 

 gas as a single series of twelve. But twenty-four jars in a single 

 series, do not give so much gas as when they form a double se- 

 ries of twelve. Again, thirty-six jars in one series, do not give 

 so much gas as when they are formed into a treble series of 

 twelve. Hence, a series of twelve of the&e jars seems to be about 

 the best unit of intensity for acidulated water. Other compounds 

 will require other Mmteq/'m^e?^5^Yl/ to produce maximum effects — 

 and other batteries will require different extent of series to pro- 

 duce the same unit of intensity as that produced by the jars. 



"As far as my knowledge extends, I cannot point out any elec- 

 tro-magnetic apparatus so likely to suit you as those described in 

 Vol. xLiii of the Transactions of the Society of Arts. They are 

 those I still operate with, and I am not aware of any improved 

 method of showing the principal experiment. Those described by 

 Dr. Page are very neat, and might answer for the lecture table 

 very well. Almost every experimenter has some piece of appa' 

 ratus of his own contrivance, but I think there are none of much 

 use to you beyond those made public." — ^Letter to Prof. Silliman, 



Art. IV. — Facts relative to the temperature of the year, as dedu- 

 ced from a sei^ies of observations made at Amherst College, in 

 1839 ; by Prof. E. S. Snell. 



Wishing to ascertain as nearly as possible the mean temperaw 

 ture of this place, and likewise to determine what two or three 

 daily observations would furnish that mean for the several sea- 

 sons of the year, I proposed to the students, at the beginning of 

 1839, to commence a series of hourly observations of the ther- 

 mometer. Nearly all the members of the college very cheerfully 

 and generously engaged in the plan, each individual in his turn 

 yecording the temperature twenty-four times in as many success- 



