44 
deny the entity of heat, to account for the alternate exhibition 
and extinction of the thermoinetric heat, that is, in fact, 
evolved and absorbed by those mutations of water. 
The Author again referring to the long standing con- 
trovercies concerning the essential nature of heat, stated that 
more than one hundred works have been published on the 
subject during the last 200 years, and yet no conclusion has 
been arrived at, as to the soundness of either of the original 
theories above cited, nor have any discoveries been made that 
explain the agency of heat, in the mutations of water, since 
the days of Bacon and Boyle, with the sole exception of 
those of Dr. Black, which appear to prove its latent state in 
bodies. And since we have no settled doctrine as to its 
essence, we must allow that the subject is of philosophical 
interest, and especially this branch of it concerning latent 
heat, in defence of which these notes are offered. 
The President said that some very interesting experi- 
ments made by Mr. Dyer, many years ago, were in favor of 
the dynamical theory of heat, which he believed to be fully 
able to explain the phenomena ascribed by Black to “ latent 
heat.” 
A Paper was read by Dr. R. Angus Smith, “ On the 
Production and Prevention of Malaria.” 
The Author did not pretend to enter on the whole subject, 
but to give a few observations which he considered fitted for 
its illustration. — Malaria has unquestionably been proved to 
be caused by the decomposition of organised bodies. If so, 
it must exist to some extent everywhere. By the mode of 
testing the air invented by the Author, every place tried at 
home and abroad was found to have some oxidizable matter 
in it, although in some this was extremely small. In such 
cases the matter was probably oxidized to a state in which 
it would be innocuous. This oxidizable matter no doubt 
rises, in a great measure, from vegetation. Vegetation does 
not merely grow ; it dies. This death may be caused by 
