294 
NATURE 
[May 23, 1912 
’ 
(9) Dr. Pring’s ** Laboratory Exercises "’ covers 
a rather narrow range of experiments in physical 
chemistry, but the book has the advantage that 
many of the experiments are well worth doing, 
and are not included in more conventional text- 
books. The use of Junker’s gas calorimeter, the 
Mahler-Cook combustion bomb, and the Wanner 
pyrometer, together with experiments on the 
charge and discharge of an accumulator and on 
electrolytic oxidation and reduction, provide a 
course of real value both as an education in 
method and as a training in operations of great 
technical importance. , Such a course affords a real 
inducement to a student to enter the Manchester 
laboratory, offering as it does exceptional oppor- 
tunities for technical training on lines widely 
different from the ordinary course of work in 
physics or in physical chemistry. eines 
OUR BOOKSHELF. 
Prehistoric Thessaly: being some Account cf 
Recent Excavations and'Explorations in North- 
eastern Greece from Lake Kopais to the Borders 
of Macedonia. By A. J. B. Wace and M. S. 
Thompson. Pp. xvi+272+vi plates. (Cam- 
bridge: University Press, 1912.) Price 18s. 
net. 
Messrs. Wace AND THOMPSON have opened a new 
chapter in the history of early civilisation. They 
have shown that in northern Greece a Neolithic 
culture, with a peculiar geometric art of its own, 
held the field contemporaneously with the Bronze 
Age “Minoan” and “ Agean” culture of southern 
Greece until the latter had reached its final phase 
and was entering upon its decline. Bronze was 
not used by the prehistoric Thessalians until the 
“Third Late-Minoan Period” of the ASgean cul- 
ture, when they finally accepted its use from the 
southerners, not earlier, probably, than circa 
1300 B.¢., and not very long before iron came into 
general use. This is a most revolutionary dis- 
covery, and its effect upon the supposed history of 
the development of the use of bronze in the rest 
of Europe cannot yet be gauged. M. Tsountas, 
the distinguished Greek archeologist, had already 
discovered important remains of the Neolithic 
Thessalian culture, with its remarkable poly- 
chrome geometric pottery, at Dimini and Sesklo, 
but he had failed to detect its remarkably late 
date. He placed it on the usual a priori grounds 
anterior to the Bronze Age Minoan civilisation 
merely because it was Neolithic. The discovery 
of Messrs. Wace and Thompson, for which they 
give chapter and verse in this book, is a much- 
needed rebuke to a priori arguments in dating 
prehistoric antiquities. 
I regret that considerations of space forbid me 
to say more of the book, which is a fine one. In 
it the authors have given us not merely a descrip- 
tion of their own work, but a comprehensive 
monograph upon all the recent excavations in 
NO. 2221, VOL. 89] 
northern Greece, including those of Tsountas and 
Sotiriadis, which have inaugurated this new know- 
ledge of early European civilisation. 
Ei Resear 
Gem-stones and their Distinctive Characters. By 
Dr G. F. Herbert) ’smithy  Ppm exvepsnes 
(London: Methuen and Co., Ltd., 1912.) Price 
6s. net. 
Turis compact and well-illustrated manual sup- 
plies a want which has long been felt. So many 
minerals have been found, in recent years, to fur- 
nish varieties characterised by brilliant colours, 
with exquisite transparency and lustre, that 
jewellers have now a much wider choice than 
formerly in making selections for their artistic 
productions. It is unfortunately true that the 
use of these new gem-stones is greatly hindered 
by popular prejudices in favour of the materials 
with an old-established reputation, but a work like 
the present is calculated to bring home, both to 
the artists in jewellery and the public served by 
them, the wealth of unexploited material at com- 
mand for ornamental purposes. 
The early chapters of the book, describing the 
characters of gem-stones and the methods of dis- 
criminating between different species, are charac- 
terised by simplicity, clearness, and accuracy. 
Among the chapters on technology, that which 
is perhaps of greatest interest deals with the 
manufacture of precious stones. The method by 
which true rubies are now regularly produced for 
the market is not only fully described, but is illus- 
trated by a photograph of the apparatus actually 
employed. The author is, however, able to show 
what means are available for discriminating 
between the natural and the artificial gems, and 
he adds: “At the time the manufactured ruby 
was a novelty, it fetched as much as 6l. a carat, 
but as soon as it was discovered that it could 
easily be differentiated from the natural stone, a 
collapse took place, and the price fell abruptly 
to 30s., and eventually to 5s. and even Is. a carat. 
. The prices of the natural stones, which at 
first had fallen, have now risen to almost their 
former level.’”’ The wise caution is still insisted 
on, however, of Caveat emptor. 
In the descriptive part of the book an attempt 
at classification of gem-stones is made, which will 
probably not meet with very general acceptance. 
The title of ‘ precious-stones” is only allowed to 
the diamond, ruby, sapphire, and emerald. The 
large group of “semi-precious” stones includes 
(with the topaz, spinel, peridot, zircon, opal, &c.) 
many beautiful substances which up to the 
present have been little used. The remaining 
classes are the ‘ornamental stones”? and the 
“organic products ”—pearl, coral, and amber. 
An important feature of the work is the number 
of illustrations given in it. Besides those in the 
text, there are thirty-three plates, three of which 
are in colour, giving a fair idea of the appearance 
of the gems in their natural and cut conditions. 
J. W. J- 
ae 
