BELLANI’S MAXIMUM THERMOMETER.--This thermometer is represented by pl. 4, fig. 9. Take a tube which is very regular, and about one-eighth or one-twelfth of an inch diameter in the bore; solder a reservoir at each end, one of them much larger than the other; make a bend near the large reservoir, and then fill the instrument with alcohol to A. Above that, place the first index, which consists of a very small piece of tube closed at one end and cut off square at the other. In the interior of this tube the two ends of a hair are fixed, by means of a little rod of iron, which is pushed into the tube. Introduce a quantity of mercury above this index, make the bend B, add again mercury as far as C, then another index similar to the first. Finally, fill the rest of the tube and the half the little reservoir with alcohol, and seal the point. * * * * * DIFFERENTIAL THERMOMETER.--This instrument is represented by pl. 3, fig. 14. Take a tube ten or twelve inches long, and one-eighth or one-twelfth of an inch internal diameter; blow a bulb at one end, and bend the tube at a right angle towards the fourth part of its length. Prepare a second tube in the same manner, and solder the bent ends together, so as to form a single tube with a bulb at each end, having previously poured into one of the bulbs a small quantity of sulphuric acid tinged red. Instead of following the above method, you may take a single tube of twenty or twenty-four inches in length, and of the above-mentioned diameter; you solder a bulb at each end, bend the tube twice till it represents the figure, pour in the acid, and then seal the open points. The graduation of the differential thermometer, as well as of all the other thermometers, is described in a subsequent section. * * * * * TUBE FOR CRYSTALLIZING SPERMACETI.--Take a little capillary tube; curl one of its ends into a ring, and solder the other to a cylindrical reservoir, two-thirds of the capacity of which you fill with very pure spermaceti dissolved in sulphuric ether; you then seal the point of the reservoir. See pl. 3, fig. 27. * * * * * TUBE FOR DEMONSTRATING THE NON-CONDUCTABILITY OF HEAT BY LIQUIDS.--This is represented by pl. 2, fig. 26. It is a tube sealed at one end, bordered at the other, and bent in such a manner as conveniently to permit the upper part of a column of liquid to be exposed to heat. * * * * * TUBE FOR ESTIMATING THE DENSITY OF VAPOURS.--Represented by pl. 2, fig. 14. It is merely a tube sealed at one end, bordered at the other, and bent as shewn by the figure. * * * * *