by the Boiling Point of Water. 289 
copper-pan for holding water, Fig. 1, plate VII., with three 
moveable wite-legs. The bottom is flat, so that the flame 
of a spirit-lamp plays fully upon it. This lamp or furnace 
consists of two parts, a flat dish or saucer, Fig. 3, containing 
a little alcohol, which is set on fire, and then covered by the 
double dome-shaped vessel, Fig. 4, also of thin copper, with 
an air-tight plug a, by which a certain quantity of spirit of 
wine is introduced, and the lower part communicating with 
a bent tube or nozzle 6, by which alcohol in ebullition is 
violently projected by the pressure of its own vapour, when 
heated by the flame in the saucer. The jet of burning spirit 
thus thrown up like a volcanic explosion through the aperture 
of the dome, has such force as to resist the blast of a hurri- 
cane, and plays right upon the bottom of the cylindric boiler 
‘or pan. Two fluid ounces of spirit of wine will thus boil 
above a pint of water in still air in four minutes; and I have 
frequently first melted snow, and then brought it to boil to 
the amount of a pint, with little more alcohol, but, of course, 
in a longer time. 
The furnace and boiling apparatus, together with a reser- 
voir of alcohol, packs into the copper-pan, and that into a 
cylindrical leather case 4 inches high, and 6 in diameter. 
The thermometer, Fig. 2, is carried separately. It is 15 
inches long and the degrees measure ;3, inch, which is quite 
sufficient in practice. Parallax is avoided, by having the 
scale repeated on each side of the tube on two pieces of copper 
not in the same plane. 
Fig. 5 represents the spirit measure, Fig. 6 a reservoir for 
spirits, Fig. 7 a water measure or cup, Fig. 8 a handle which 
opens all the plugs, and serves also for lifting the lamp and 
pan when heated. 
I immediately saw the value of the apparatus for deter- 
mining the boiling point, and directed Mr Adie to adapt a 
thermometer to it, graduated from 185° to 214° of Fahrenheit’s 
scale, divided to 10ths of a degree, the divisions admitting 
an estimation to 100ths. I am well assured, however, that 
in no circumstances, even the most favourable, is the observa- 
tion true to less than ,\; of a degree. But this quantity 
corresponds to only 25 feet of elevation. and is therefore, 
VOL. XXXVIII. NO. LXXVI.—APRIL 1845. 3 
