JuLy 20, 1899] 
NATURE 
269 
and Linde systems are very similar, and work “ precisely 
on the same lines.” The truth is that the Linde ap- 
paratus works with air at three pressures, uses pre- 
liminary refrigeration by ice and salt, has widely coiled 
helices consisting of three pipes placed concentrically 
one within the bore of another, and takes from two to 
three hours to liquefy air; while the Hampson and 
Tripler plants, working from a compressor, both have air 
at two pressures only ; both use no preliminary refrig- 
eration, both have simple pipe closely coiled, and both 
liquefy air in less than fifteen minutes. It would there- 
fore have been more correct, since the Hampson 
machine is the older of these two, to change the names 
used by Dr. Sloane, and say that the Tripler apparatus 
“is very simple, and resembles very much the” Hamp- 
son “apparatus, and it works precisely on the same 
lines.” 
The salient feature of the book, as a historical summary 
and appreciation, is the glorification of Mr. Tripler and 
American invention. The greatness of Mr. Tripler’ 
achievements is compared to his advantage with the 
paltry efforts of European experimenters in many places, 
as on pp. 255, 289, 290, 355, and 356; and on p. 
296 he is roundly called ‘the originator of the self- 
intensive system.” Dr. Sloane’s repeated use of the 
phrase “back of” instead of “behind” suggests that he 
is probably an American ; and if that is so, patriotism 
might be allowed to excuse the over-laudation of a 
fellow-countryman in cases of real merit. It cannot, 
however, justify the ascription of unreal achievements: 
Mr. Tripler did not show to the public his liquid air 
made by the self-intensive method till 1897, nearly two 
years after that method had been published and fully 
described in Europe; and as he has produced no 
evidence of having used it privately before, he cannot 
be accepted as its “originator.” Dr. Sloane, it is true, 
in a summary of Mr. Tripler’s work as the inventor of 
the self-intensive process, says on p. 288 that ‘‘ about 
1891 air was liquefied” by that gentleman. If this be 
true, both Dr. Hampson and Dr. Linde must give up 
their claims to priority ; but something more than this 
vague and unsupported statement is necessary to prove 
that Mr. Tripler had invented the process before 
November 1894 and May 1895, the earliest authenti- 
cated European dates for the invention. It is indeed 
inconceivable that, if:Mr. Tripler had understood the 
subject well enough to invent and successfully work the 
process in 1891, he could in 1893 have devised the futile 
and absurd scheme described in his patent of that year 
referred to above. Mr. Tripler’s later apparatus, too, is 
insufficiently explained and authenticated if his claims to 
the invention of it are to be seriously considered. Dr. 
Sloane must know that the chief interest of this process 
centres in the arrangements for expansion and interchange 
of temperatures, and in illustrating the European systems 
he very properly gives sectional views which clearly 
explain the nature of these arrangements. But in illus- 
trating Mr. Tripler’s machine, while he gives needless 
views and descriptions of the rooms, the people, and 
such well-known appliances as three-stage compressors, 
coolers, and washers, he shows only the outside of the 
vitally important interchanger. Why did not Dr. Sloane 
ask for sectional views of this and of the mysterious 
NO. 1551, VOL. 60] 
“special valve, the invention of Mr. Tripler”? We could 
then have judged how far they really differ from those 
shown and used in Europe nearly two years before. He 
informs us in the preface that his requests for assistance 
in the compilation of his book met with quick response 
from Mr. Tripler among others. In connection with 
liquid-air processes there has been too much mystery 
made, the public being freely asked for their admiration 
and faith without being frankly made acquainted with 
the details of an inventor’s process and the evidence of 
his originality. Strangely enough Dr. Sloane, who so 
complacently accepts Mr. Tripler’s mysteries, is himself, 
on p. 238, an objector to their prevalence in similar work 
at the Royal Institution. So much attention has lately 
been excited by Mr. Tripler’s scheme for using liquid air 
as a means of providing unlimited power without cost, 
that Dr. Sloane might fairly have been expected to give 
his unscientific readers some useful guidance by explain- 
ing how these schemes violate hitherto inviolable laws 
as to the latent heat of volatilisation of gases, and are, in 
fact, blunders due to a mistaken interpretation by Mr. 
Tripler of one of his experiments. Instead of this. Dr. 
Sloane, on p. 289, gives Mr. Tripler’s schemes a mild 
approval and support by saying that 
“the utilisation of the low-grade heat energy of the uni- 
verse presents nothing essentially impossible. This heat 
Tripler hopes to utilise. If itis utilised, &c... .” 
Such toleration of Mr. Tripler’s amazing proposals 
would disqualify any writer as a serious scientific critic. 
A MANUAL OF ANTHROPOLOGY. 
The History of Mankind. By Prof. Friedrich Ratzel. 
Translated from the second German edition by A. J. 
Butler, M.A. ; with Introduction by E. B. Tylor, D.C.L, 
F.R.S. With coloured plates, maps, and illustrations. 
Three volumes. Pp. xxiv+ 486+562+599. (London: 
Macmillan and Co., Ltd., 1896.) 
(Re. student of anthropology will welcome this hand- 
some English edition of Prof. Ratzel’s “ V6lkerkunde’ 
as an invaluable work of reference for the numerous and 
scattered branches of his study. Perhaps no department 
of science embraces so large a field as the study of man 
and the history of civilisation, and in proportion to its 
complexity the greater is the necessity for some general 
guide to the subject. On the first publication of the 
work in the years 1885-88 it was at once recognised as 
the most comprehensive survey of the state of our know- 
ledge of the lower races of mankind that had hitherto 
appeared, and since that time it has maintained its posi- 
tion in Germany as the standard popular work on the 
subject. The present English translation has been made 
from the second German edition. and may therefore be 
regarded as in all essentials abreast of recent research. 
In his Introduction, Prof. Tylor has called attention to 
the large number and accuracy of the illustrations with 
which the book is furnished, and which he well remarks 
surpass in excellence any that have yet been issued in 
similar works intended for general circulation. The im 
portance of good illustrations in contrasting the succes 
sive stages of the development of the human race cannot 
be over-estimated, for they convey far more to the general 
