262 
Notices of Books. 
[Aug. 
In the account of Leslie’s Differential Thermometer, the writer might have omit- 
ted half what he has written, and considerably improved the article; for, first, the 
instrument is of very limited applicability ; and, secondly, the graduation of it, as 
devised by the inventor, is erroneous 2 . In the great variety of objects to which this 
instrument has been recommended to be applied, we can almost fancy a profes- 
sor’s pen emulating the magic weapon of Harlequin ; and we think a very little con- 
sideration sufficient to satisfy any one that, as in the instance of the wooden sword, 
the transformations are more curious than useful. Thus has Professor Leslie 
made this child of his fancy at once a Differential Thermometer, a Hygrometer, a 
Photometer, a Pyroscope, and an vEtherioscope. “ ’Tis every thing by turns and 
nothing long 3 but if after considering this versatility of character and list of 
its performances, we ask cui bono ? the answer must be, that, excepting to illustrate 
the subject of radiation of heat, we really know of no use that the instrument can 
be turned to. It is a bad hygrometer, (even supposing its scale corrected,) a worse 
photometer, a most lame and inconclusive pyroscope, (the common thermometer 
much better,) while as an setherioscope, it is merely a substitute for the latter 
instrument, with the advantage (if that be one) of giving a little mystification to 
the subject. But there are deficiencies as well as exhuberances ; and our great 
quarrel with this article is, that the subject of it being heat, we have no attempt to 
put the question of thermometry on a sound basis ; and lastly, we have not even 
an allusion to the curious laws of cooling discovered by MM.Dulongand Petit. 
We should be sorry to be misunderstood in these our crude remarks on the 
proceedings and publications of a Society which we so highly honour. It may 
perhaps strike the influential members of it, should they ever chance to see these 
strictures, that faults there must be when even our puny optics can discern them. 
Nevertheless, as before remarked, our complaint is not that they are not better 
than other treatises on the subject, but that they are not so good as the Society 
have the means of making them. On the contrary, let any one compare the trea- 
tise on heat, against which we have started so many objections, with any other 
even our most celebrated, and he will find that it is a far more satisfactory per- 
formance. , If he wish to be thoroughly mystified on the subject, let him turn to 
Thompson’s Chemistry. The article in Brewster’s Encyclopaedia is little better. 
In lire’s Chemical Dictionary, article Caloric, he will find one of the best accounts 
previously published ; yet, in comparing it with the present, the reader will be 
sensible of its deficiencies. Dr. lire’s style, too, is rather ambitious and figurative 
for the details of science. Rhetoric is here misplaced, and only serves to° dazzle 
weak minds, and persuade them that the author means more than meets the eye. 
In Leslie’s much talked of treatise, it is quite extraordinary how the author has 
contrived to shut his eyes to the simple truth which was staring him in the face 
all the time. This remark is more particularly applicable to his hygrometrical 
- researches; though it is not inapplicable also to those on heat. It is something 
more to the purpose to say that there is not one of his pretended laws, whether of 
heat or moisture, which has not been proved to be erroneous. 
Upon the whole, therefore, though falling short of what we could wish to see 
them, and what we believe they could he made, we can safely recommend this 
series of publications to the student, as affording him at a very moderate price, 
perhaps better diges ts of what is known in the various branches of science, than he 
wall be able to find in more expensive works. 
- See D. B. s communication on this subject in our 13th number, vol. ii p 24. We 
nad once occasion to compare the indications of Leslie’s Thermometer with a common 
one, and were surprised to find they did not correspond, although we failed to perceive 
tne cause o t the discrepancy at the tune. r 
rios ('I!? 0 ri 0 have purchased the hygrometers, photometers, pyroscopes, and aethe- 
eauafiv ir.?! -J? 1 lessor, will, we apprehend, find the second part of our quotation 
tovs wfth J h * e au , d d «T er , to t - ,e ! r §' reat mortification that these curious 
the house of e Ilames > a |' e only ht for deposit in that museum which is to be found in 
and crionled 7 experimental philosopfier-that limbo of superannuated instruments 
’ m whlC !\ are la,d U P cracked retorts, broken-necked thermo- 
it was Yhe bnsines P u, nps, . and b arou| eters that have suffered from wind. We think 
thrdisin JSS n a Society for promoting useful knowledge, to have prevented 
Save to* | e m-iker co . ns . e( l ueut to le purchase of instruments which are of no use 
transferrino- monev , . nrenl ™>“ d a «swer no earthly purpose save that of 
«dd, thaiST hVl the,r J J 1 ock f. tsfroia those of the ill advised purchaser. We may 
they w they as useful as they are the contrary, they are so hio-h priced that 
*ney would be pronounced unconscionably dear iii # b pnwu 
