BY JAMES TOLSON, ESQ. aE 
scientific knowledge exists, and accordingly much money 
has been uselessly expended on them. 
In the following notes, in which are incorporated extracts 
from the works of our most eminent scientific writers on 
the subject of heat, I have endeavoured to bring together 
the information necessary to form a clear conception of 
what heat is and the processes with which we have to deal 
whenever we deprive a body of its heat. The most recent 
views also on decomposition and putrefaction are glanced 
at as dealing with a subject that seems to be almost 
neglected, though involving considerations of the utmost 
importance to the successful carrying out of the work. 
Special attention should be directed to them by all who are 
making the subject a study. A clear conception of 
the laws which govern these processes can be obtained 
without any great amount of study, and my aim is to bring 
into as compact a form as possible the leading principles, 
leaving the scientific explanation of them for the after 
investigation of those who wish to obtain a deeper insight 
into the subject. 
It will be convenient to deal with the subject under the 
following heads :— 
1. The nature of heat, including its transmission and the 
laws of cooling. 
2. Decomposition and the germ theory. 
3. Refrigeration practically applied. 
Heat.—“ Heat,” in the language of Tyndall, ‘‘is not the clash 
of winds ; it is not the quiver of a flame, nor the ebullition of water, 
nor the rising of a thermometric column, nor the motion which 
animates steam as it rushes from a boiler in which it has been 
confined. All these are mechanical motions into which that of 
heat may be converted ; but heatitself is molecular motion. The 
molecules of bodies, when closely grouped, cannot, however, 
oscillate without communicating motion from one to another, and 
it is the propagation of the motion of heat from molecule to 
maolecule to which we must devote our attention. 
‘Ideas concerning the nature of heat have recently undergone a 
great change. Formerly this agent was regarded as a species of 
matter, but of the class of imponderables, since no evidence of 
the weight of heat could be obtained, inasmuch as a hot body 
does not weigh more than the same body when cold; but very 
