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342 Proceedings of the British Association. 
a. 3 
I may here repeat what I stated elsewhere, that by employing 
platinum instead of copper, the sega expenses may be re- 
— in the proportion of nearly 23 to 
. The consumption of zine, which al place while the ma- 
a is at rest, and does no work at all,.is double that which oc- 
curs while it is producing the maximum of power. 
T consider that there will not be much difficulty in Aeterna 
ing with sufficient precision, the duty of one pound of zinc, by 
its transformation into the sulphate, in the same manner that in 
the steam engine, the duty of one bushel of coal serves asa 
measure to estimate the effect of different combinations. The 
future use and application of electro-magnetic machines appear 
to me quite certain, especially as the mere trials and vague ideas 
which have hitherto prevailed. in the construction of these ma-_ 
chines, have now at length yielded to the precise and definite. 
laws which are conformable to the general laws which nature ; 
accustomed to observe with strictness, whenever the question 
effects and their causes arises. In viewing on the one handa 
chemical effect, and-on the other a mechanical effect, the inter- 
mediate term scarcely presents itself at first. In the present case, 
it is magneto-electricity, the admirable discovery of Faraday, 
which we should consider as the regulating power, or as it may 
be styled, the logic of electro-magnetic machines. 
Prof. Kelland read a paper having for its object to point out the 
state of our experimental knowledge of the transmission of heat, 
and to exhibit its total inadequacy to serve as the test of any pre- 
cise and accurate theory. 
r. Anderson made a communication concerning the meteorol- 
ogy of Perth. This place is about 30 feet above the mean level 
of the ocean, in lat. 56° 23’ 40” N.; lon. 3° 26/20” W. The 
magnetic variation there, (which Seeaeci to have reached its max- 
imum in 1815,) was 26° 54’ W. in Nov. 1836: the magnetic dip 
was 72° 10’ in May, 1838. The mean barometrical pressure de- 
duced from a period of consecutive observations, continued from 
1829 to 1835, was 29.802 in., the time of observation being nine 
o’clock in the morning. The extreme range of the barometer du- 
ting this period was 2.821 inches. The mean temperature is 
about 48° F. The mean annual quantity of rain from 1829 to 
1834 was 30.89 inches. 
