MarcH 17, 1904] 
NATURE 
473 
Some interest attaches to the preparation of optically 
active hydrocarbons of the benzene series as described by 
Messrs. Klages and Sautter in the Berichte. A dextro- 
rotatory hexenylbenzene, C,H,.CH : CH.CH(CH,).C,H,, 
having [a],+50°3, was prepared by condensing amyl iodide 
with benzaldehyde by Grignard’s magnesium method, and 
this was reduced to a hexylbenzene, 
C,H,.CH,.CH,.CH(CH,).C,H,, 
which gave [a])+17°-2. The latter compound behaves in a 
normal manner as a homologue of benzene, and it should, 
therefore, be possible to prepare from it optically active 
derivatives of all the most important types. 
THE additions to the Zoological Society’s Gardens during 
the past week include a Snow Leopard (Felis uncia) from 
Tibet, presented by Major Cox; a Lesser White-nosed 
Monkey (Cercopithecus petaurista) from West Africa, pre- 
sented by Mrs. Gower; a Mozambique Monkey (Cerco- 
pithecus pygerythrus) from East Africa, a Yellow Baboon 
(Papio cynocephala) from Africa, a Green Monkey (Cerco- 
pithecus callitrichus) from West Africa, a Ring-tailed Lemur 
(Lemur catta) from Madagascar, a Common Rat Kangaroo 
(Potorous tridactylus) from Australia, a Lesser Vasa Parrot 
(Coracopsis nigra) from Madagascar, a Blossom-headed 
Parrakeet (Palaeornis cyanocephala), two Larger Tree 
Ducks (Dendrocygna major) from India, deposited; two 
Himalayan Pheasants (Lophophorus impeyanus) from the 
Himalayas, purchased. 
OUR ASTRONOMICAL COLUMN. 
A Srx YEAR PERIOD FOR THE POLAR Motion.—Writing to 
the Astronomische Nachrichten (No. 3932), Mr. H. Kimura, 
of the International Latitude Station, Mizsusawa, states 
that he has found that the x and y curves of the polar 
motion return to the same phase (not amplitude) every six 
years. ‘This is shown very clearly on the curves accompany- 
ing the note. : 
The latest maximum deviations of the instantaneous pole 
occurred in 1891 and 1897, whilst the minima deviations 
were in 1894 and 1900. 
The actual x and y curves obtained from the observations 
may be fairly represented by calculated curves derived from 
the combinations of two periods of 438 days and 365 days 
respectively. 
During his researches on this subject Mr. Kimura has 
discovered that there are important systematic variations of 
purely local character which are as yet unaccounted for. 
Dovuste Star OsserRvATIONS.—During his absence on 
leave from the Hong Kong Observatory, Prof. Doberck has 
observed 280 double stars, mostly taken from the Struve 
catalogues. The name, coordinates, position angle, and 
distance of each pair are given in a list published in Nos. 
3830 and 3831 of the Astronomische Nachrichten as a con- 
tinuation of the previous list which appeared in Nos. 3860 
and 3861. In cases where there are more than two com- 
ponents in any one system, the angles and distances 
between each pair are given. The observations were made 
at Copenhagen. 
CORRECTIONS TO THE BERLINER JAHRBUCH FUNDAMENTAL 
CataLocuE.—In Nos. 3927, 3928 and 3929 of the Astrono- 
mische Nachrichten, Dr. A. Auwers publishes the results of 
his discussion of the observations, made between 1750 and 
1900, of the 622 stars of the Astronomische Gesellschaft 
Fundamental Catalogues, which were published in the 
Berliner Jahrbuch in 1883. After a lengthy discussion of 
the reduction of the observations, Dr. Auwers gives a table 
showing the total corrections to the places for 1875, and 
then discusses several multiple systems, for each of which 
he gives the elements he has computed. In a second table 
he compares the corrections and the hundred-year proper 
motions given in his tables with those given by Boss, for 
each five degrees of declination and right ascension. 
NO. 1794, VOL. 69] 
COOPERATION IN SOLAR OBSERVATIONS.—In No. 1 (1904) 
of the Memorie della Societa degli Spettroscopisti Italiant 
Prof. Ricco discusses the modern methods of studying solar 
phenomena, and points out the vital importance of obtain- 
ing as full a record as possible of all the changes which 
take place in the sun. He also describes the results 
obtained by Prof. Hale with the spectroheliograph, and 
directs attention to the important connections which have 
recently been shown to exist ketween solar and meteor- 
ological changes. 
A VSLUDY VOR HE RADIO-ACTIVITY. OF 
CERTAIN MINERALS AND MINERAL 
WATERS 
Part I. 
CONSIDERABLE number of minerals are known in 
varying degrees to be radio-active. Lists have been 
given by M. and Madame Curie (‘‘ Thése présentée a la 
Faculté des Sciences,’’ Paris, p. 19) and by Sir W. Crookes 
(Roy. Soc. Proc., vol. Ixvi. p. 411). Except in the case of 
pitchblende, little has been done to determine the nature 
of the radio-active constituents, or to decide whether any 
hitherto unknown radio-active body is present. 
To obtain complete information on these subjects, the 
only method available would be completely to analyse the 
mineral, and examine every precipitate and filtrate for radio- 
activity. This process is, of course, very tedious, and the 
results have to be interpreted with care, since traces of 
radio-active elements may often be carried down in the 
groups to which they do not properly belong, and thus 
cause confusion. A much easier method is to heat the crude 
mineral, and to examine the rate of decay of the emanation 
which it gives off. Each emanation has a characteristic 
time constant of decay, and by determining this we can 
identify it. 
The method is, of course, useless for testing the presence 
or absence of radio-active elements such as uranium ~ 
which do not give off a characteristic emanation. But the 
great facility with which it may be applied to a small 
quantity of material, and the definiteness of the results, are 
great merits. 
In any case when a material suspected to contain radium 
is obtainable in abundance, it is better to test for the 
presence of emanation than to look for activity in the 
solid. For but little of the solid material can be advan- 
tageously used in the test. Thick layers give no larger 
effect than thin ones, since the upper layers absorb the 
radiation from the lower. But the emanation can be ex- 
tracted from any desired bulk of -material, and the effect 
proportionately increased. If carbonic acid or any other 
gas is evolved at the same time in inconvenient quantities, 
it can be absorbed with a suitable reagent, and the eman- 
ation contained in it thereby concentrated. 
The present paper gives the results of an examination of 
certain radio-active materials by this method. 
No new emanation has been recognised. The results 
have in all cases been attributable to thorium and radium. 
If any emanation decidedly more permanent than that of 
radium existed in the evolved gas, the method could not 
fail to detect it. For in every case the activity of the gas 
was watched until it became comparable with the very 
small activity due to the walls of the vessel. If a more 
durable emanation had been present even in small quanti- 
ties, the proportion of it present would have increased 
relatively to the radium emanation, and its presence would 
have become apparent towards the end by a diminished 
rate of decay. 
Small quantities of an emanation less durable than that 
of radium might have escaped detection. For they would 
have been masked by the much greater quantity of the 
latter. 
By measuring the rate of leak due to the accumulated 
1 By Hon. R. J. Strutt, Fellow of Trinity College, Cambridge. Read 
before the Royal Society, March ro. 
2 Ihave found a distinct, though feeble, emanation from recrystallised 
uranium nitrate, having a rate of decay equal to that of the radium 
emanation. Whether this is really due to uranium, or to traces of radium, 
which the uranium still contains, must be left for the present an open 
question. 
