Analyses of Books . 
149 
(! The fusing points of pure metals are determinate, and unchangeable, they also 
comprehend nearly the whole scale of temperature ; the non-oxydable metals alone 
embrace a range from the low melting point of silver to the high ignition of platina. 
Thereare, it is true, only three fixed points in this scale, but as many intermediate 
linksmay be made as are required, by allowing the three metals together in different 
proportions. When such a series has been once prepared, the heat of any furnace 
maybe expressed by the alloy of least fusibility which it is capable of melting. 
Besides the uniformity of the determinations which such a pyrometer would give, 
several other advantages might be enumerated : — the smallness of the apparatus, 
nothing more being necessary than a little cupel containing, in separate cells, eight 
or ten pyrometric alloys, each of the size of a pin’s head; the indestructibility of the 
specimens, since those melted in one experiment would need only to be flattened 
under the hammer to be again ready for action ; and the facility of notation, since 
three letters, with the decimal of the alloy, would exp ess the maximum heat. Thus 
Pyrom. S. ,3, G. might be used for an alloy of 0,7 silver with 0,3 gold, and G. ,23 
P- would express gold containing 23 per cent, platina. 
“ As gold melts at a heat not very much above silver, I assumed only 10 degrees 
between them, measuring each by a successive addition in the alloy of 10 per cent, 
of gold to the pure silver, the t nth degree being of course measured by pure gold. 
These alloys are easily made, and require no comment :in accurate researches, they 
may he further subdivided, using always the decimal notation. 
“ From the fusion of pure gold to that of pure platina, I assumed 100 degrees, 
adding 1 per cent, of the latter metal to the alloy, which measured each successive 
degree. Now it is hardly to be supposed, that the progress of these hypothetical 
degrees represent equal increments of he.it; they will, however, as I before observed, 
always indicate the same intensity ; and their absolute value, as a matter rather of 
speculative than of practical interest, is to be sought by other expedient.’ ^ 
The foregoing extract sufficiently explains the principle of Mr. Pnnsep s pyro- 
meter. We are sorry, we can only find room for the naked results, and must pass 
over a great deal of interesting discussion on points of collateral interest, vve 
strongly recommend the paper to the perusal of those at all interested m pyro- 
metrical questions. ,, ... ,, , 
Max. Alloy Melted 
Muffle of an assay furnace, front. 
Muffle of an assay furnace, middle, 
Muffle of an assay furnace, 
The Calcutta charcoal is better than the Benares, and freqi 
heats the muffle to 
Melting point of copper by two trials under the muffles, 
Calcutta silver melting furnaces of the English construe 
Black lend table furnace, without chimney, 
Calcutta open native furnace, 
Calcutta blast furnace for melting musters, 
Apex of condensed air blow -pipe flame, 
Melting point of cast iron, about 
Highest heat of a forge with the Benares charcoal, 
Tlie second object of pyrometrical inquiries, the referring any fixed 
^temperature' ’to Fah^nheit's scale has, we think been 
f hls experimentalist. The air thermometer has been proposed as a me s of 
measuring JnVb teinnerature and if made with a bulb of platina it wouldembrace the 
Jjde of the slleTf hm and include tl.e highest temperatures we can command. 
i,r ^ffi°X 8 d U t Engu“r e in lndlrthereTa'favailaUe^ Srer a sufficient 
above'dlemelt^g^^ of the appara^tus, we must 
refer ,k„ „ v , heen already more than our limits can 
justify. They auDen’r to e f f been every way unexceptionable : the scale of the 
er he’d °cca 'iff 80 f ‘ 
r™ *. — display, 
' The bulb of t bi s thermometer contained 1M0 Bs. north otgold. 
s 
,0 
G. 
s. 
,3 
G. 
s. 
,5 
G. 
r G. 
,03 
P. 
G. 
,04 
P. 
G. 
,075 P. 
G. 
,08 
P. 
G. 
,06 
P. 
G. 
,20 
P. 
G. 
,20 
P. 
G. 
,30 
P. 
G. 
,55 
P. 
