Fuly 20, 1871] 

and Dr. Pole, it appears, wrote for him the rather jejune 
algebraic investigation of the principles of such machines, 
which, when we come to examine it, we find is merely 
what we may find in any elementary book on pneumatics ; 
and owing to the omission of all the s¢vuctural conditions 
producing loss of effect in blowing machines, exists, in fact, 
as a mere parade of useless symbols, of no value to the 
constructor or the purchaser or the user of such apparatus. 
Now we are wholly unable to see the necessity for thus 
cumbering with a needlessly hooked-on subject a book on 
Iron Metallurgy at all; but if otherwise, then it should 
have been gone into thoroughly, and in a way to be of real 
value to the constructor. To have done this, however, 
would have required some fifty pages or more, so that a far 
better mode, in our judgment, would have been to have 
simply confined the point to a reference to the great mono- 
graphs which exist on this special subject, both theoretic 
and practical. Neither Dr. Percynor Dr. Pole seems to have 
been aware of the fact that a quite exhaustive investi- 
gation of the theory of blowing machines (omitting none 
of the conditions of practice) and of high merit, was pub- 
lished as long ago as 1805, by Herr J. Baader, Counsellor 
of Mines of the Kingdom of Bavaria, and which was 
specially and by the authority of Napoleon I. translated into 
French and published in the Azzales des Mines in 1809. 
There may be such a thing as apparent completeness, 
which yet is only the piling together of incongruity or of 
incompleteness. 
But this want of the sense of balance and of relative 
importance is not confined to such collateral subjects of 
practice. Dr. Percy, in the volume here noticed, devotes 
nine pages to the physical properties of lead, in com- 
mencing, and of these we find four (under the head of 
Resistance to Pressure) are occupied with details of 
Coriolé’s fruitless attempts in 1829 to construct weighing 
machines, whose indications were to be derived from the 
compression suffered by known volumes and forms of lead 
pieces—a subject as indirect and foreign to the physical 
properties as it is far away from the metallurgy of lead, 
One statement made in this part of the volume is un- 
doubtedly incorrect, where it is said, “by hammering 
lead becomes harder, but acquires its original softness by 
annealing.” The actual fact is, that lead cannot be made 
harder by hammering, for its annealing temperature is so 
low (that of every metal being a function of its fusing 
point), and it suffers so large a deformation by reason of its 
softness when hammered, that enough heat is evolved 
by internal work to cause the metal to anneal itself,—in 
other words, never to become harder. This has been fully 
ascertained, and the fact has even been taken practical 
advantage of by those engaged in “ drawing lead pipe” 
by the older methods, who are well aware that a hard 
pinch at first or rapid reduction in diameter in passing 
through the holes of the draw-plate, heating the lead, 
enables it to be drawn into finished pipe with a less total 
expenditure of power than if drawn slowly and with so 
gradual a reduction in diameter as that the lead should 
remain always nearly cold. Were the lead hardened here 
by a compression quite the same in effect as hammering, 
the very reverse must be the case. This volume comprises 
avery good account of the Pattinson process for sepa- 
ration of silver, and also of Parkes’s zinc process. What 
can have induced Dr. Percy (who is, we believe, fond of 
NATURE 
2190 

scholarship) to employ such barbarous compounds as 
“ lithargefication,” “desilverisation,” and “ decopperisa- 
tion,” in place of “disargentation,” ‘“ decuperation ” ? 
What would be thought of “ desugarification” as a sub- 
stitute for “ desaccharisation”?—but these are matters 
of taste and no more. 
The chapter on the ores of lead and that on the assay of 
lead ores are amongst the very best in the volume, which 
is beautifully printed with the clearest of type and paper, 
and with goodindices. There are nine pages near the end 
devoted to poisoning by lead, which, though certainly not 
the metallurgy of lead, may prove of some use to those 
employing work-people in lead smelting or manufacturing 
operations ; though we think here, perhaps, the wisest in- 
structions might have been simply, “‘send the patient to 
the doctor.” We have little confidence in amateur or 
improvised medicine on the part of “laymen,” in such 
cases as lead-poisoning, at any rate. On the whole, though, 
as we have had to: point out, this work of Dr. Percy’s 
is not free from faults, it is, we think, in several ways the 
best of all those on Metallurgy which have appeared from 
under his pen, and in the collection and discussion of a 
vast array of facts is a noble volume, the very best that 
yet exists in English on its subject. 

NEWMAN’S BRITISH BUTTERFLIES 
An Illustrated Natural History of British Butterflies, 
By Edward Newman, F.L.S., F.Z.S., &c. 8vo. (Lon- 
don: W. Tweedie, 1871.) 
HE British Butterflies form a small but striking group 
of insects, and hence not only are they as a general 
rule the first objects on which the collecting spirit of the 

RED ADMIRAL (Pyrameis Atalanta). Upper side. 

Under side. 
young entomologist is exerted, but they also offer one ot 
the best means of commencing the study of entomology. 
Thus they are easily collected and preserved, their appear- 
