342 Pi'oceedings of the British Association. 



I may here repeat what I stated elsewhere, that by employing, 

 platinum instead of copper, the theoretical expenses may be re- 

 duced in the proportion of nearly 23 to 14. 



5. The consumption of zinc, which takes place while the ma- 

 chine is at rest, and does no work at all, is double that which oc- 

 curs while it is producing the maximum of power. 



I consider that there will not be much difficulty in determin- 

 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 as a 

 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 is 

 accustomed to observe with strictness, whenever the question of 

 effects and their causes arises. In viewing on the one hand a 

 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. 



Dr. 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. ; Ion. 3° 26' 20'' W. The 

 magnetic variation there, (which seemed 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 barom.eter du- 

 ring 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. 



