tal 
i. 1894. 
ise was to be ascribed to the atmosphere. 
upon receiving the great news, Pascal hastily 
‘ict and gave to the world the knowledge of 
ret. It is the reproduction of this herald of 
sovery that Professor Hellmann has given us. 
again re-published, but was incorporated 
ered in the ‘‘Traitez de |’ Hauilibre des 
c., published in 1663 by Perier, one year after 
ch. Hence it is usually believed that the 
ave us the first account. 
known, it is believed by many writers that 
dsuggested these experiments to Pascal, and, 
nade that claim in two letters of 1649 to 
scal, as he expressly states in his ‘‘ Récit,” 
“horror vacui” up to the time of the suc- 
sion of Perier’s experiments, nor did he ever 
tes’s statements. After weighing all the 
efully, Professor Hellmann believes he has 
Mr. Mourisson, who in his recent work’ 
nst Pascal. Whatever may be the truth, the 
hat Pascal first gave this important discovery 
that no little credit must be given Perier for 
is care (He even surrounded himself with 
that “‘none could deny”) with which he 
2 experiments, and that Professor Hellmann 
earned the praise of the whole scientific 
ting at the command of every one such a 
ecuted copy. 
‘@ Argent. Par H. Gautier. 
arse Fils; 203 p., 1893: 
ge aes Oljectifs Photographigues. Par E. 
Paris, Gauthier-Villars et Fils, Quai des 
ugustins, 196 p., 1893, Broché, 2 fr. 50, 
Mea ft. 
these works relates to the preparation and 
> precious metals, and to their monetary and 
In the preliminary part the author gives a 
yf the chemical and physical properties of 
1etals and of those metals with which these 
alloyed. The principal alloys used in coin- 
relry are described, together with the legal 
ised upon them. It is very instructive to 
‘ely this official circumspection is carried on 
1 we are forced toregard the looseness cur- 
2a with much dissatisfaction. The second 
ok is devoted to the purely practical side of 
describing methods of refining and of as- 
_as of analysis by the wet method. 
as aimed to make his ‘‘Choice and Use of 
Objectives” essentially a practical discus- 
all act as a guide to the professional and 
grapher alike, assisting them both in the 
-r lenses and giving an insight into the requi- 
cessful picture. The book is rather more 
adicates, for, without being abstrusely scien- 
one to an excellent theoretical as well as 
ledge of the photographic apparatus. 
Points in the Science of the Earth. By Sir 
Aan IDawisom, (CoMie, ILIL.IDE, imeReSee 
2tc. New York, Harper and Brothers. 
d, 469 p., 1894, $2. 
Jameson, a friend and co-worker with Mur- 
vick, Phillips, Logan, Gray, Lyell, and, 
1 those historians of the earth’s past who 
nuch to elevate mankind and to bring him 
f his Creator’s greatness, Sir J. William 
; no introduction to an English-speaking 
ways exhibiting a true Christianity and re- 
mos‘ speacialized researches a wonderful 
Paris, Gau- 
2n e* Philosophe, etc.”’ Paris, 1888. 
“= SCIENCE. 
conception of the great tri 
endeared Himself to many 
those who have devoted 
geology. ‘‘Vhe Earth ay 
World,” ‘“‘Science in Bibl 
library, and his many purely 
valued aids in all geologic 
““The present work (we qu 
that is new and much in correction and amplification o1 
that which is old; and is intended as a closing deliverance 
on some of the more important questions of geology, on 
the part of a veteran worker, conversant in his younger 
days with those giants of the last generation, who, in the 
heroic age of geological science, piled up the mountains 
on which it is now the privilege of their successors to 
stand.” In the rush of modern thought; in the fia dv 
stecle annihilation of all that has been laboriously erected 
by our teachers, we are too often liabie to forget that 
these edifices have a foundation which it will profit us to 
study. In the narrowness of our progress we see only 
an architecture incompatible, we believe, with the condi- 
tions of our greater knowledge, and hence we reject the 
same to build for ourselves higher structures, may be, 
but too often with a sacrifice of solidity, to brilliancy and 
originality of design. It is, then, exceedingly wholesome 
to take up such a work as the present and to be reminded 
that there are some, with an experience that few of us can 
hope to attain, who still cling to the fundamental theories 
with all the vigor of youth, and who remain undisturbed 
by the gyrations of modern scientific philosophers. In this 
“closing deliverance’ by Sir William we find a series of 
chapters each gracefully dedicated to one of those whose 
labor and life have been given in corresponding research. 
The subjects discussed are indicated in the title, being 
those great problems which have presented themselves 
from the dawn of our extended understanding of the 
world’s history; the process of world making, the first life, 
the nature of the geological record, the genesis and suc- 
cession of the earth’s fauna and flora, the cause of climatal 
change, the great ice age and pre-historic man—these are a 
few of the ‘‘ Salient Points” which will interest all, whether 
scientists or laymen in the perusal of this charming work. 
Conférences Publiques sur la Photographie. Organisées par 
LE DIRECTEUR DU CONSERVATOIRE NATIONALE DES 
Arts Ev Metrers. Paris, Gauthier-Villars et Fils. 
545 p-, avec 198 figures et 9 planches, 1893. 7 fr. 
50. 
THE above unique work embraces nineteen lectures on 
Photography organized by the eminent Colonel Lausse- 
dat, Directeur du Conservatoire des Arts et Metiers, and 
delivered at that institution during the years 1891-92. 
Each lecture or conférence constitutes a monograph in 
its particular subject and in every case has been written 
by a specialist and originator in that subject. The lec- 
tures are here reprinted in the order of their delivery, and 
though atext-book graded arrangement is not possible 
the work as a whole is a complete and most valuable 
treatise on both theoretical and technical photography. 
Photography is essentially a French science, an art of 
French invention and in France is carried to its greatest 
perfection. In fact, nowhere else has it been made, or 
rather acknowledged to be, so truly a science or so worthy 
of scientific study and experiment. The contrast is par- 
ticularly marked when comparing photographic literature 
of our own country, for instance, with the literature of 
the same subject in France. Of the many admirable 
works there recently published none will be likely to find 
more pleased readers than will this present yolume of 
conférences. It is impossible even to attempt a synopsis 
of the many subjects treated, but the titles of a part at 
