MADE IN THE EFFICIENCY OF STEAM ENGINES IN CORNWALL. 127 
a cylinder of 80 inches did 75’6 28000, exceeding the duty performed in 1 795 
in the proportion of 3.865 to 1, or as 27 : 7 nearly : and exceeding the standard 
atmospheric engines of 1778 by 10.75 : 1. But subject as in former times to a 
great variation between different engines apparently similar in all respects ; 
the average being about forty-one million and a half. 
Greatly as we are indebted to Mr. Watt for his improvement of the steam 
engine used in exhausting water from mines, our obligations to him are still 
greater for originating and carrying almost to a state of perfection, the appli- 
cation of steam as a moving power to machinery, in all the complicated and 
varied uses of mechanical inventions in this country. 
In effecting this most important object, the double engine was first brought 
into use, the extremely ingenious contrivance for producing parallel motion 
was invented, and the principle of centrifugal force enabled an apparatus 
called a Governor to regulate a supply of steam inversely proportionate to the 
velocity which might at any instant be acquired ; and the use of fly-wheels, 
perfectly understood in theory, became subservient to the regularity of motion, 
and to the gigantic efforts of our most ponderous machinery. We owe further 
to Mr. Watt the introduction, at least into general use, of what is termed be- 
velled geer. 
When wheels acting on each other by means of teeth have their axes parallel, 
the teeth however curved on themselves, must obviously be parallel also on 
their line of contact. But when the axes are inclined, the line of contact 
between the teeth should then be directed to the point where the two axes 
would intersect, thus assimilating their action to that of a cone revolving round 
a centre on a circular plane. 
Having on various occasions had my attention drawn to the consideration 
of machines forced into rapid action by great powers moving at a compara- 
tively slow rate, I have been induced to make endeavours for ascertaining the 
amount of friction in several instances. 
The mode adopted has been to impart equal velocities to the machine per- 
forming the work for which it was destined, and in a state disincumbered from 
all extraneous impediments, and then to compare the forces applied under 
these different circumstances. The media of communication being in all cases 
axes with wheels, impelled by teeth, or cogs. 
In some instances the friction was found to equal two-thirds of the whole 
