Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 4, 1802).djvu/230

below the point of boiling heat.
Fahr. 212 203 194 185 176 167 158 149 140 131		Reaum. 80 76 72 68 64 60 56 52 48 44	Fahr. 122 113 104 95 86 77 68 59 50 41		Reaum. 40 36 32 28 24 20 16 22 8 4
below the natural freezing point.
Fahr. 32 31 30 28 26 24 23 22 20 18		Reaum. 0 0.44 0.88 1.77 2.66 3.55 4.— 4.44 5.33 6.22	Fahr. 16 14 12 10 8 6 5 4 2 0		Reaum. 7.11 8.— 8.88 9.77 10.66 11.55 12.— 12.44 13.33 14.22

From this comparative view, it will appear that nine degrees of Fahrenheit's (between the point of natural freezing, and that of boiling heat), are equal to four of Reaumur's computation:—hence the scale of the former may be reduced to that of the latter, by multiplying the number of degrees above 32 (because 32 must be subtracted from the whole number given) by 4, and dividing the product by 9.—On the other hand, if the given degrees be multiplied by 9, and the product divided by 4, Reaumur's scale may be reduced to that of Fahrenheit.—Upon these principles, the preceding tables are calculated, with two decimals only below the freezing point. But, if any intermediate degrees be wanted, they may be easily ascertained, by a similar arithmetical process.

It would be needless to describe the various thermometers invented during the last century; because the two instruments before mentioned have received almost universal sanction; few others being at present employed, either by artists or men of science. Hence we shall merely observe, that De L'Isle, at Petersburgh, contrived a new thermometer, in 1733, which is divided into 50°.—Prof. Christin, of Lyons, proposed a scale of 100 equal parts between the freezing and boiling points: this division was adopted by Prof. Celsius, in Upsala, whose improved scale, consisting of 100 exact degrees, is generally used in Sweden.

There are many other thermometers, among which, those by Ducrest of Geneva; by Strohmeyer and Brander, in Germany; by Grubert in France (who, together with the three preceding, contrived the Universal Thermometer, which contains the comparative scales of 28 different instruments); by De Luc; Renaldini; Cavendish; Königsdörfer; Mudge; the Bernoullis'; Fontana; Achard; Lichtenbebg; Landriani; Saussure; Castelli; and Luz.

The first idea for constructing a metallic thermometer, or properly, pyrometer, was furnished by Graham, and improved upon by Mortimer, Ingram, Count Löser, Fitzgerald, Felter, and at length brought to perfection by Wedgewood. This ingenious manufacturer (of the finest earthen-ware from basaltic masses, or terra-cotta) has rendered an essential service to society, by his method of

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