292 
NATURE 
[JANUARY 24, 1907 
But he wisely points out that the Simplon is only 
one of a series of enterprises of the same kind, and 
while there have been improvements in the methods of 
working, as well as in the use of better explosives, the 
merit of originality belongs more properly to what 
is commonly known as the Mont Cenis tunnel. 
Tourists to whom the name Fréjus represents a 
town on the Riviera will be somewhat surprised to 
find this tunnel described as the Galleria del Fréjus, 
which appears to be its correct name. In addition to 
this, the St. Gothard, the Arlberg, and other well- 
known tunnels, the author describes several minor 
borings not commonly noticed by tourists, but which 
possess points of special interest; for example, one at 
Laveno, on Lago Maggiore. The result is a volume 
of 1228 pages (excluding tables), and a second volume 
of plates, which form a striking contrast to the small 
Manueli Hoepli of the same publisher. When we come 
to eighty pages of ‘‘ Final Considerations,’” we cannot 
help being reminded of the typical interminable sermon 
of our early days, and the analogy is further increased 
by finding 115 pages of ‘‘ appendix to the final con- 
siderations ’’ to follow. But all the same, the author 
cannot be accused of long-windedness. ‘There are a 
great many details connected with the boring of a 
tunnel, such as the rate of progress through different 
rocks, temperature conditions, descriptions of the 
machinery and of the accommodation for the 
workpeople, which interest not only the engineer, 
but also the general reader, and it cannot be said 
that the author has encumbered his subject with un- 
important or uninteresting details to any appreciable 
extent. The only exception we notice is that the tables 
of mean temperatures of such places as Venice, Alassio, 
and San Remo do not appear to have much bearing 
on the Simplon tunnel, under which heading they are 
tabulated. The text would have been handier had it 
been bound in two volumes. 
From the same publisher we have the fourth volume 
of Brioschi’s works, comprising mainly papers con- 
tributed to the Lincei Academy (1885-18096), the 
Comptes yrendus (1858-1878), and miscellaneous 
jeurnals, together with the preface and notes written 
for the Italian translation of Cayley’s ‘‘ Elliptic Func- 
tions.’? The papers for this volume have all been 
edited by Profs. Francesco Gerbaldi and Ernest Pascal, 
and the volume is uniform in style with its prede- 
cessors. In view of the rapid growth of mathemati- 
cal literature, one cannot help wondering, however, 
if it is desirable to publish collected works in such an 
irreproachable style. This reflection is suggested 
partly by the fact that though one or two English 
transactions have recently appeared with larger pages 
than formerly, they do not contain a corresponding 
increase in the number of words per page, though 
there is a great increase in their weight. And it 
should be the object of the purchaser to obtain 
Brioschi’s works, not merely to buy good paper and 
printing. 
The series of Manueli Hoepli, published in the form 
of pocket-books, numbered goo volumes in April last. 
Among the latest ones dealing with technical appli- 
cations of science we have before us two books on 
gas engines, both written by authors living in Venice, 
NOMO43. VOL. 75\] 
and containing respectively 160 and 162 woodcuts. 
The objects of the books, as stated in the prefaces, are 
nearly identical. Both authors point out that while 
other countries have advanced greatly in. the study 
and construction of gas engines, the subject has re- 
ceived little attention in Italy. Curiously enough, 
Signor Calzavara, who is a gas engineer, says less 
about the question of gas than Signor Laurenti. The 
latter’s book is divided into three parts, the first deal- 
ing with the combustibles (illuminating gas and 
heating gas, or ‘‘ gas povero,”’ as it is called in Italy), 
the second with gas generators, and the third with 
the gas engines themselves. On the other hand, 
Signor Calzavara only devotes a single chapter to 
the gas question. This chapter is, however, a long 
one, and it must be remembered that he has written 
several previous books on gas and gas motors. 
Other differences may be noted. Thus Signor Cal- 
zavara gives a really full bibliography, while Signor 
Laurenti’s book contains more numerical data in the 
form of tables. Signor Laurenti goes into detail re- 
garding cams; the other author only just refers to 
distributors without discussing the cam. Signor Cal- 
zavara considers that a ‘‘ poor gas’’ engine, with its 
own generator, cannot be used efficiently for instal- 
lations of less than 25 horse-power; Signor Laurenti 
fixes the limit at 15 horse-power. These are the 
differences one would expect to find in two books 
written on the same subject by different authors, and 
they show that anyone interested in the subject would 
derive undoubted advantages from having both books 
for reference. Gaia B: 
“ 
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