On Water-Pressure Engines for Mines. 5 
barometer and thermometer are noted at the time of each 
experiment, but such have not been taken into my calcula- 
tions above. In any repetitions of these interesting experi- 
ments, it seems to me desirable, that the pitch should be 
ascertained more exactly, by means of the beats made with 
a standard pipe, previously and accurately tuned, by a’com- 
bination of concords (or by beats) near to the proper pitch: 
_ for which previous calculations and preparation the inter- 
vals above deduced may prove of some use. 
On the Solution of Water in Air, as affecting the Barometer ; 
on Electricity, Sc. 
Your ingenious correspondent Mr. Richard Walker, at 
page 376 of your Number for November, in speaking of 
the application of the barometer as a means of indicating 
the weather, alludes to the alleged solution of watery va- | 
pour in atmospheric air, and mentions ** the dense state of 
the airbeing fittest for the chemical combination above men- 
tioned,” a rare state of the air being less capable of re- 
ceiving the water into chemical combination ;” and yet, lower 
down in the same page we find it said, that the air ‘* is in- 
capable (by having become colder) of retaining or suspending 
it (water) ina stale of chemical combination ;” as though 
colder air were not more dense than warmer air! 
In the next page, contrary to the opinion of that veteran 
meteorologist M. De Luc, we find, that atmospheric elec- 
tricity is to be considered ** rather as a miatter of ‘curious 
speculation than of practica! utility!” As an antidote to 
such reasonings and principles of meteorology as these, I 
beg to refer your readers to an able and original view of 
these subjects, lately taken by M. De Luc, in Mr. Nichol- 
son’s Journal of Natural Philosophy, vol. xxvil. p. 244. 
On Water- Pressure Engines for Mines. 
I beg to inform Mr. John Taylor, or the gentleman who 
communicated on the subject of hydraulic pressure-engines 
for pumping mjnes, vol. xxxvi. page 394, that it is a mistake 
to say, that * none have yet been successfully made upon a 
large scale,” because Mr. Trevethick in 1803 erected one in - 
Crash-purse Lead Mine, half a mile south of Yolgrave in 
Derbyshire, by the fall of 144 feet, of a branch of the 
Lathkil river, into the famous Hellcar Sough, which has 
ever since cflecthally pumped that mine 48: feet below the 
sough, and enabled large profits to be obtained by the 
owners, instead of the ruin that had previously attended the 
“concern, as the name implies. And further, that the steady 
’ A 3 * and 
