sphere are due. 

May 12, 1923] 
NATURE 
635 

When considering the theory of anticyclones and 
cyclones, it is better to pay attention to the great 
permanent features shown by the distribution of 
atmospheric pressure over the earth’s surface. It 
is to these that the prevalent winds of the atmo- 
Small travelling cyclones are of 
course interesting; and, strange to say, they show 
the same peculiarities of pressure and temperature 
_ distribution as do the much larger permanent cyclones. 
Everything points to the conclusion that there is 
some other force at work more potent than the 
temperature conditions in the troposphere; and I 
have suggested that this force arises from differences 
of temperature in the upper stratosphere. 
It is true that many registering balloon ascents 
show an isothermal condition in the lower strato- 
sphere ; but others show quite a rapid rise of tempera- 
ture with increasing height. A study of these curves 
_ led me to conclude that at a height of 60 km. the 
temperature approaches very nearly that of the 
earth's surface. That such is the case a study of 
_ meteoric phenomena has demonstrated. Now if the 
distribution of temperature near the limits of the 
upper atmosphere varied with the latitude, the 
pressure distribution at the earth’s surface would be 
affected. It seemed natural to suppose that such 
heating would be greater over the equatorial than 
the polar regions; but if this were so, the low- 
pressure areas would be in low latitudes and the 
high-pressure areas in high latitudes; which is not 
the case. / 
The above considerations suggested that the upper 
_ atmosphere must be hotter over the poles than it 
is over the equator; for, if such were the case, all 
our difficulties in trying to account for the pressure 
distribution and directions of the winds would vanish. 
However, there are several peculiar phenomena of 
the polar areas, such as the aurora borealis, which 
require explanation as well. This is a matter which 
cannot be adequately discussed in a short letter ; 
but it is probably due to the deflexion of electrons, 
etc. (shot out by the sun), towards the polar areas 
by the earth’s magnetic field. 
It has been objected that my theory necessitates 
vertical currents in the stratosphere, which the 
temperature conditions would not permit. The 
actual temperature conditions would certainly retard 
the equalisation of pressure by vertical movements 
in the stratosphere, and this would cause it to take 
lace mainly in the troposphere. It may be that it 
is this that makes it appear as though the force 
maintaining cyclones resided at the upper surface of 
the troposphere, as Mr. W. H. Dines points out in 
one of his papers. Indeed, the inrush due to the 
friction of the air with the earth’s surface in a cyclone 
would lead to an outrush at the top of the troposphere. 
It is admitted that there are difficulties in the 
theory which remain to be explained ; but they seem 
less than those met with when other theories are 
considered. R. M. DEELEY. 
Tintagil, Kew Gardens Road, 
Kew, Surrey. 

Physical Literature on the Continent. 
DurInc the last few years it has become increas- 
ingly difficult for the universities of Central Europe 
to procure the scientific journals of other countries, 
in consequence of the calamitous depreciation of 
German and Austrian currencies. Such a state of 
things acts as a deterrent to scientific advancement 
in that the knowledge of work done outside only 
slowly and imperfectly permeates into these countries 
through indirect channels. Quite recently I have had 
NO. 2793, VOL. I11] 
two letters from continental physicists in reference to 
this matter, and I am anxious to bring the facts to the 
notice of the readers of NaTurRE, in the hope that 
something may be done to remove to some extent the 
difficulty which at present exists. 
Prof. Benndorf, of the Physical Institute of the 
University of Graz, Austria, informs me that the last 
number of the Philosophical Magazine available in 
that city is that of July to14. In view of the expense, 
it has been quite impossible for them to procure back 
numbers of this and other English scientific journals, 
or to maintain them at present, as will be realised 
from the fact that the equivalent in our money of the 
annual grant to the Physical Institute of that Univer- 
sity amounts only to 23s. The unsatisfactoriness of 
such conditions is obvious. ; 
As it is not difficult in the libraries of most of our 
university towns to procure at least one copy of the 
Philosophical Magazine, it has occurred to me that 
perhaps some reader of NATuRE might be prepared 
to assist the Graz Physical Institute, by handing over 
his copy of the Philosophical Magazine to that institu- 
tion say at the end of each month of issue. Sucha 
donation would be most acceptable, and the donor may 
be sure of the sincere gratitude of the recipients, some 
of them well known in physics, such as Benndorf, 
Kohlrausch, and Hess. 
The second letter has reference to the Physical 
Institute of the University of Berlin, which, for like 
financial reasons, is no longer in a position to 
purchase the Philosophical Magazine. Several members 
of this Institute, including Prof. Pringsheim, Dr. 
Hettner, and Dr. Laski, have suggested to me the 
possibility of surmounting the difficulty by an ex- 
change of periodicals such as has already been arranged 
with America, They propose an exchange of the 
Philosophical Magazine as issued for either the Zeit- 
schrift fiir Physik, Die Naturwissenschaften, or some 
other journal to be arranged upon. 
If any reader of Nature feels disposed to assist in 
respect of either of the above suggestions, I shall be 
glad if he will acquaint me of the fact, so that I may 
put him in touch with the Institutes referred to. 
RoBert W. Lawson. 
The University, Sheffield, 
April 18. 

Chloroplasts and Cells. 
IN an interesting account of studies with the 
variegated variety of the fern Adiantum cuneatum in 
the March issue of the Journal of Genetics, Miss Irma 
Andersson shows that the prothallia all sooner or later 
develop whitish stripes in which the chloroplasts are 
pale green and only half the size of the chloroplasts 
in the surrounding green cells. There are no inter- 
mediates, nor does any cell contain chloroplasts of 
both types. The purpose of this note is to direct 
attention to certain facts which appear to have a 
bearing on this sharp segregation occurring in gameto- 
phyte tissue. 
There is evidence from several sources that the size 
of the chloroplasts in a cell is controlled and deter- 
mined by the size of the cell, or, at any rate, that 
whatever determines the one also controls the other. 
Thus in tetraploid forms of Solanum nigrum and 
tomato produced by grafting, Winkler (Zeitsch. f. 
Bot., 8 : 417-531, 1916) has shown that the chloro- 
plasts and starch grains as well as the cells and nuclei 
are approximately twice their normal size. Similarly, 
in the tetraploid Ginothera gigas it has long been known 
(Gates, Arch. f. Zellforsch. 3: 525-552, 1909) that 
the cells and nuclei are conspicuously larger than in 
the parent form, and van Overeem has shown recently 
