Frpruary 18, 1904] 
NATURE 
LETDERS TO THE EDITOR. 
(The Editor does not hold himself responsible for opinions 
expressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NaturRE. 
No notice is taken of anonymous communications.] 
The Victoria Nyanza Jelly Fish. 
In a note occurring in your last issue (p. 348). mention is 
made of an interesting fact with which zoologists have for 
some time been familiar, namely, that the medusa 
characteristic of Lake Tanganyika exists at present in the 
Victoria Nyanza also. As it seems to be suggested that 
this discovery is in some way or another adverse to the 
theory of the origin of a portion of the fauna of Tanganyika 
for which I have been responsible, you will perhaps 
allow me space to point out that, so far from the fresh 
knowledge being in any way antagonistic to the view in 
question, the existence of the jelly fish in other lakes beside 
Tanganyika is exactly what one would, and did, anticipate, 
supposing the halolimnic theory to be correct. 
The medusa in the Victoria Lake is identical with that 
in Tanganyika, and its presence in the former can be ex- 
plained in two ways. 
It may have, so to speak, existed there from all time, in 
which case the rest of the halolimnic fauna, or at least a 
part of it, should be found along with the jelly fish. In 
this case we should have a confirmation and extension of 
the view which I have already put forward, that the ancient 
sea from which the halolimnic ‘‘ relic ’? sprang spread much 
further towards the east than was at first supposed. 
It is, however, quite possible that the medusa has been 
recently transported to the Victoria from Tanganyika, owing 
to the opening up of the new trade routes, and the carriage 
of water in gourds and other vessels from one basin to the 
other. 
This second view, to me, seems extremely likely, and it is 
certainly supported by the fact that the Victoria jelly fish 
is identical with that in Lake Tanganyika. Had it been 
long isolated in the former lake it would almost certainly 
now have presented specific differences, just as the fresh- 
water shells of the Victoria differ slightly from those of the 
neighbouring lake basins. J. E. S. Moore. 
Royal College of Science, London. 
The Blondlot z-Rays. 
THERE can be no doubt that the results obtained by M. 
Blondlot and others at Nancy are most remarkable, even if 
they should prove to be, as Herr Lummer’s communication 
to the Berlin Physical Society would lead us to suppose, 
purely subjective, or, as he prefers to put it, ‘* objective 
phenomena in the retina.”’ 
I have endeavoured to repeat M. Blondlot’s experiments, 
but quite without effect, using calcium sulphide screens of 
the dimensions he suggests, that is, about 16 mm. by 
2 mm. 
A thin layer of gum is spread over a sheet of cardboard 
and the powder sprinkled over the surface until as large 
an amount as possible adheres to the screen. No difference 
in the colour or intensity of the phosphorescent glow appears 
to take place when a lead screen or the hand is interposed 
between the phosphorescent screen and an Auer burner 
completely enclosed in a tin-iron box with an aluminium 
window, nor does the interposition of a quartz lens in various 
places have any effect. 
A very much larger screen was exposed to the Auer 
burner, one half being screened with lead and the other 
with thin aluminium, so that only the latter half was ex- 
posed to the radiation of the n-rays. The luminosity of the 
screen was, however, quite uniform throughout, although a 
sharp line ought to have separated the two parts of the 
screen, as the intensity of the phosphorescence should have 
been different in the two sides. 
I am at a loss to find any other explanation of M. 
Blondlot’s results than that he has come across a radiation 
to which some men are blind and others not so. 
Self-hypnotism due to fatigue of the optic nerve may 
account for results of one observer alone if he were to 
at the same time, but I think that M. Blondlot will 
have taken the precaution to get others to work the screens 
for him whilst he observed, and then compared results. 
I may perhaps venture to note that a few years ago, in 
the course of some photometric work with fluorescent bodies, 
I was led to try whether one fluorescent body would in- 
crease or diminish the brightness of another (Phil, Trans., 
vol. cxci. p. 92), but could not detect any such change 
within the errors of observation. 
The fact that M. Blondlot has actually measured the wave- 
length of the n-rays leaves little doubt (in my mind) that 
what he has observed is, in the true sense, an objective and 
not a subjective effect, but at the same time the fact also 
that so many others who have tried in apparently the same 
way have failed, and failed deplorably, leaves still less doubt 
that the precise conditions upon which the effect depends 
yet remain to be discovered. JOHN BUTLER BuRKE. 
Cavendish Laboratory, February 8. 
Radiations producing Photographic Reversal. 
In a paper read before the Rontgen Society last December 
I pointed out that the B or y rays from radium are capable 
of producing photographic reversal—a result more recently 
confirmed by Mr. Skinner, of the Cavendish Laboratory. 
Since that particular property, shared by radiations 
generally, appeared likely to furnish a test of use in dis- 
criminating between rays of various kinds, I have ex- 
amined also the reversing effect of polonium emanation 
upon photographic plates. 
I find that these rays are capable of reversing pressure 
marks, but are unable to modify the action of X-rays or day- 
light upon the plate. Neither will they, even with prolonged 
exposure, show any tendency to reverse their own photo- 
graphic effect, as happens in the case of light or rays from 
radium. 
It is remarkable that, in their power of inducing photo- 
graphic reversal, X-rays and the emanation from polonium 
appear to behave in a similar manner. 
CuarLes E. S. PHILLIPps. 
Shooters Hill, Kent, February 15. 
Radium Débris. 
Tue valuable summary of ‘‘ Researches Relating to 
Radium ”’ in your issue of January 28 contained the follow- 
ing paragraph:—‘ From the disintegration theory it 
followed that the accumulation, during past ages, of the 
final products of the change of the radio-active elements 
must exist in the natural minerals in which these elements 
are found,’’ also that helium was likely to be a product of 
the change. 
It is the final products of the disintegration which are 
interesting, for if the disintegration has been going on for 
untold ages it is likely that other elements may have been 
produced from the atomic débris. It seems quite certain 
that radium belongs to Group ii. of the periodic classifi- 
cation, and no doubt to the calcium family. Is it not 
possible that this disintegration which has been going on 
for ages has given us one final ‘‘ elementary ’’ product in 
the shape of calcium? ‘The close connection between the 
atomic weight of helium (4) and the atomic weight of 
calcium (40) suggests such an idea. Moreover, if one puts 
hydrogen in its position in the periodic classification, 
justified by its atomic weight, then helium comes into 
Group ii. along with the calcium and radium. Now, 
although it has hitherto been the rule to look upon the 
heavier elements as products of the condensation of some 
fundamental light substance, does not this atomic disinte- 
gration suggest that the lighter elements may be regarded 
as products of the breaking up of the heavier ones? When 
one looks at the list of elements, the small number of heavy 
elements impresses the mind, and the abundance of the 
lighter ones, those which one may regard as the final pro- 
ducts in atomic disintegration, is well in evidence. The 
polymerisation of the original products of atomic disinte- 
gration may be responsible for some of the numerical rela- 
tions among atomic weights. 
However, attention need not be confined to the natural 
manipulate the lead screens and to make observations | minerals in which the radio-active elements exist in order to 
NO. 1790, VOL. 69 
