186 REPORT—1840. 
The discourses of Dr. Chalmers and Dr. Alison contained frequent 
references to statistical data, but the enumeration of these would be of 
little service without a full statement of the arguments they were in- 
tended to support. 
On the excess of Population, and on Emigration as a Remedy for it, in 
the Highlands of Scotland. By Dr. Aucorn. 
On the Population of Scotland. By Mr. Witson. 
On the Libraries of Germany. By Professor ADRIAN. 
On the Parish of Dunfermline. By the Rev. P. CHALMERS. 
MECHANICAL SCIENCE. 
On the Temperature of most effective condensation in Steam Vessels. 
By J. Scort RussE tt. 
Much has been said regarding the perfection of the vacuum formed 
in the condenser of a steam-engine, especially a marine engine. It is 
a fact of great importance, and it is the result of theory, established on 
incontrovertible truth, and confirmed by experiment and by practice, 
that a vacuum may be too good, and become a loss instead of a gain. 
The truth is simply this, and should be known to every engineer: Jf 
the barometer stand at 294 inches, the standard of this country, the 
vacuum in the condenser is TOO GOOD éf it raise in the barometer more 
than 28 inches of mercury. The following is a simple proof of this 
doctrine, divested as far as possible of a technical form, and put in the 
shape of an inquiry into the best state of a condenser :— 
Let ¢ = the caloric of water of 1°; 
c = the constituent calorie of water in the state of steam ; 
e =the total force of steam in the boiler, in inches of mer- 
cury; and 
x = the elastic force of steam at the temperature of best con- 
densation, which we seek to discover. 
Then, from the law which connects the elastic force of steam with 
