January 8, 1914] 
NATURE 
We can scarcely expect more from it than this; for 
the test of convergence of a given series is ultimately 
whether s, has a limit, s, being the sum of the first n 
terms, and there is no reason to suppose that we can 
find, in all cases, another and more manageable way 
of expressing the condition of convergence. Mr. 
Tavani gives several important references, and has 
had the advantage of criticisms by Prof. M. J. M. 
Hill and Mr. G. H. Hardy. 
Recent low-temperature research has led to results 
which it is difficult to reconcile with the belief that at 
the absolute zero of temperature the energy of the 
atoms and molecules of bodies vanishes. The change 
of the specific heat of hydrogen at very low tempera- 
tures has been shown by Prof. Einstein and Dr. Stern 
to be consistent with the energy of the molecules being 
finite at the absolute zero. Prof. Onnes and Dr. 
Keesom come to the same conclusion with regard to 
the translatory energy, and Dr. Keesom has shown 
that some of the difficulties of the theory of free 
electrons in metals are removed by the assumption 
of finite energy at the absolute zero. According to 
a recent communication from the physical laboratory 
of the University of Leyden, Dr. Oosterhuis finds it 
necessary to assume a finite energy of rotation of the 
molecules at the absolute zero in order to correlate his 
observations of the magnetic susceptibilities of a 
number of paramagnetic substances at very low tem- 
peratures. By this means the deviations from Curie’s 
law of constancy of the product of susceptibility and 
absolute temperature are explained. 
In a paper in the Atti R. Accad.. Lincei (vol. xxii., ii., 
p- 390) Mr. C. Acqua shows that nuclear degeneration 
is produced in plant cells by traces of uranium salts. 
If, for example, wheat plants are grown in very dilute 
solutions of uranyl nitrate (1 in 10,000), the rootlets 
soon cease to develop, and this is accompanied by 
the production of a yellow colour in the nuclei of the 
cells of the meristem, which at the same time no 
longer stain in the usual manner with hemotoxylin. 
The action of the uranium brings about destruction of 
the chromatin, and the cessation of nuclear activity. 
The cause of this is not yet ascertained, but it is 
suggested that it may be the formation of organo- 
metallic compounds or the radio-activity of the 
uranium itself. 
Tue Chemical Society’s Journal contains an impor- 
tant contribution, by Messrs. Pickard and Kenyon, to 
the study of optical rotatory power in homologous 
series. Of the series of secondary alchohols from 
C.H;.CHOH.CH, to C.H,.CHOH.C,;H;,, one is 
necessarily inactive, but all the others with one excep- 
tion have been prepared and isolated in an optically 
active form. The molecular rotatory powers in this 
remarkable series of compounds increase fairly regu- 
larly when once the inactive diethyl carbinol 
C.H,.CHOH.C,H,; has been passed, but somewhat 
excessive optical activity appears in the fifth and tenth 
members of the series. There might be some tendency 
to ascribe this small excess of rotatory power to ex- 
perimental error, but for the fact that when the 
B30 
alcohol the curve of increasing rotatory power loses 
all pretence of uniformity, and develops a series of 
remarkable humps, which culminate at the alcohols, 
C,H;-€HOH.C,H,,, C.H;.CHOH.C,,H.,, and per- 
haps C.H,.CHOH.C,;H;,. This curious behaviour is 
attributed to the fact that the “growing chain” of 
carbon atoms probably assumes a spiral form, each 
loop of the spiral containing five carbon atoms. Some 
indication of the same qualities has been detected in 
solutions of the methyl-carbinols, CH,.CHOH.R, but 
the isopropyl-carbinols, (CH,),CH.CHOH.R, behave 
in a perfectly regular manner, both in the homo- 
geneous state and in solution. 
WE learn from The Engineer for January 2 that 
the French Minister of Public Works has requested 
the railway companies to submit proposals for equip- 
ping the cabs of express locomotives with audible 
signals as soon as possible. The Minister also points 
out the terrible consequences resulting from the em- 
ployment of gas for lighting the coaches whenever a 
train is smashed in collision. He therefore orders the 
railway companies to hasten the substitution of elec- 
trical for gas lighting on fast trains, and he further 
states that he will henceforth refuse permission to 
the companies to purchase rolling stock equipped for 
gas lighting. It may be noted that British railway 
companies are giving attention to the automatic con- 
trol of trains. Some are trying mechanical means 
of placing fog-signals on the line when the sema- 
phore is at danger; others, like the Great Western 
and the North-Eastern, have cab signals already in 
use, and some are testing electrical apparatus. Many 
people hold that it is better to leave full responsibility 
with the driver, and not transfer it to a mechanism 
which may fail. Public opinion will, however, prob- 
ably force automatic control on British railway com- 
panies. 
LEcTurRERS in colleges and teachers in schools will 
welcome the publication of the second part of Messrs, 
Newton and Co.’s catalogue of lantern slides. The 
volume, which is effectively bound in cloth, runs to 
nearly six hundred pages, and gives full particulars 
of the immense variety of slides which this firm is ~ 
able to supply to illustrate lectures and lessons in 
science, nature-study, geography, history, the various 
industries, and other subjects. The increase in this 
department of their business has led Messrs. Newton 
and Co. to open their New Lantern Slide Gallery at 
37 King Street, Covent Garden, W.C. It is worthy 
of note that many of the sets of slides cata- 
logued have been compiled by such educational autho- 
rities as the Visual Instruction Committee of the 
Colonial Office, the Committee of London Teachers 
of Geography, and so on, and purchasers have the 
assurance that the slides are particularly suitable for 
educational purposes. The number of slides dealing 
with scientific subjects is very large, and many of them 
represent important pieces of research. As _ typical 
may be mentioned those from photographs of flying 
bullets by Prof. C. V. Boys, of sound waves by Prof. 
R. W. Wood, of ripples by Dr. J. H. Vincent, and of 
alcohols are merely dissolved in benzene or in ethyl j astronomical work in the Solar Physics Observatory. 
NO. 2306, VOL. 92] 
