Trials of Portable Steam-Engines at Cardiff. 
55 
goino; ships ylionld bo required to pnss some examination, and tlio Council 
tliink it desirable that this opinion should be communicated to the Board of 
Trade. 
I have the honour to be, Sir, 
Your obedient Servant, 
(Signed) C. W. Merrifield, ' 
The Secretarj% The Board of Trade, Hon. Sec. 
Whitehall Gardens, S.W. 
Tlie other Society has not, up to the present time, come to a 
conclusion upon the matter. 
The before quoted letter of the Naval Architects to the Board 
of Trade is abundant proof, if proof were wanted, that the 
settling of what shall be considered a Commercial horse-power, 
is among the most difficult problems that can be brought before 
a practical body ; at least it appears so to those who have 
tried to solve it, but to those who have not, it seems extremely 
simple. 
A barrister lately said to the same writer of this Report, 
You surely do not mean to tell me that you do not know what 
a horse-power is, you, that have been a mechanical engineer all 
your life ! " The answer given was — " Indeed, I do not, there 
is a difficulty in the outset ; what sort of horse-power do you 
mean .'' 
" Why, I mean a horse-power." 
" I know you do, but there are five kinds of horse-power." 
" Five kinds ! impossible, it can't be." 
" But there are : I will give you the names and the nature of 
them." 
" 1st. The real horse-power, the power of a horse, estimated 
to lift 22,000 lbs. 1 foot high per minute. 
" 2nd. That which in James Watt's time was called the 
Nominal horse-power, a horse-power of 33,000 lbs. raised 1 foot 
high per minute, which power he gave to all his early engines, so 
that the purchaser, having one-and-a-half times the power of a 
good horse, should not be in a position to complain of the engine 
as inadequate. 
" This term Nominal is now commonly confounded with the 
Commercial horse-power, and the name. Theoretical horse-power, 
is substituted to represent the received scientific horse-power of 
33,000 foot-pounds. 
" 3rd. The Gross Indicated horse-power. This is the whole 
power developed on the piston of the engine, without any deduc- 
tion for friction, which power divided by 33,000 gives the Gross 
Indicated horse-power. 
"4th. The Net Indicated horse-power. This is the same as 
the foregoing, minus a certain allowance for friction. 
