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- 
jars in a double series of twelve, give about twice as much 
gas as a single series of twelve. But twenty-four jars ina 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 these jars seems to be about 
the best unit of intensity for acidulated water. Other compounds 
will require other wnits of intensity to produce maximum effects— 
and other batteries will require different extent of series to pro- 
duce the same wnit 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. xin of the Transactions of the Society of Arts. They are 
those I still operate with, and Iam not aware of any improved 
method of showing the esineeel 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. 
Arr. IV.—Facts relative to the temperature of the year, as dedu- 
ced from a series of observations made at Amherst College, in 
1839; by Prof. BE. 8. Sneu. 
Wisuine to ascertain as nearly as possible the mean tempera- 
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 
recording the temperature twenty-four times in as many success- 
