
aed 
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June 30, 19 
NATURE 
881 

and insist upon, higher standards. The planter of 
the future must be taught to think and to understand 
his economic and biological universe. This is 
realised at the West Indian Agricultural College, but 
are we going to live up to it? Will such an outlook 
receive the Suppo of tropical public opinion on 
which we are so largely dependent for funds ? Is it, 
for the present, to be expected? It is therefore 
important that the matter should be appreciated by 
scientific opinion in this country to which scientific 
workers in the Crown Colonies look very largely for 
encouragement and protection. 
Reference to research has been purposely avoided 
in the above observations for the sake of simplicity. 
But research, the mother of scientific education, has 
also its disabilities in the tropics. Up till quite 
recently, the demand, the popular demand, has been 
for ‘‘trouble-curing’”’ rather than research. The 
present danger, however, is that research work may 
be interfered with through depriving investigators of 
their time in order that they may give instruction. 
W. R. DUNLOP. 
West Indian Agricultural College, 
14 Trinity Square, E.C.3. 

Gravitation and Light-Pressure in Nebulz. 
In Nature of June 16 there is a most interesting 
letter by Dr. Jeans on my suggestion that spiral 
nebula may consist of dust repelled from the stars 
___by light-pressure. My original note must, I fear, 
have been somewhat misleading to have called forth 
the particular criticism which Dr. Jeans’s letter 
contains. As was, I think, brought out in the 
discussion at the Royal Astronomical Society, it 
was never my intention to suggest that the dust 
clouds are so thick that there is any appreciable 
shielding ; indeed it is perfectly obvious, as Dr. 
Jeans points out, that the whole theory would break 
down unless the particles are assumed to be so far 
apart that they can be treated individually. 
The misunderstanding is due to a somewhat 
ambiguous sentence at the end of the paper, which 
I admit is capable of giving quite a wrong impres- 
sion. I had anticipated that my suggestion would 
be criticised unless I presented some explanation of 
the so-called ‘‘ nove” in spirals. The suggestion 
put forward was that they were similar to terrestrial 
meteoritic showers. In order to show that this was 
not impossible I put in some very rough quantities, 
and endeavoured to show that they would not lead 
to absurd results for the characteristics of the nebula. 
The density found, based, it may be remarked, upon 
the time in which the meteoritic stones are supposed 
to evaporate, leads to a mass over the depth of one 
light-year of o'r grams per square centimetre. I 
agree, of course, that this cannot be supported by 
radiation pressure; indeed a remark by me to the 
same effect may be found in the Observatory some 
years ago. It would have been better had I said 
that this result was some 10* times too high in view 
of the obvious transparency of parts of the spirals. 
The great uncertainty of the quantities used, how- 
ever, emboldened me to say this was of the right 
order of magnitude; compared with the results 
derived from other hypotheses to account for the 
“ nove,’’ which led to results 1o* times greater, this 
was perhaps excusable. 
Dr. Jeans’s criticism, to which I admit my some- 
what optimistic sentence laid me open, applies, 
therefore, to that part of my paper from which this 
unduly large mass was decir ; t.e. the hypotheses 
introduced to account for the “ nove.’’ It is possible 
that the quantities which I used might be altered 
NO. 2800, VOL. I11] 
| plausibly to give a more acceptable value. It is 
perhaps even more likely that a more satisfactory 
hypothesis may be evolved to account for the 
phenomenon. But the main outlines of my suggestion 
do not seem to be controverted. 
F. A. LINDEMANN. 
Clarendon Laboratory, Oxford, 
June 16. 

The Heape and Grylls Rapid Cinema. 
Ow1ne to arrangements deemed necessary at the 
Soirée of the Royal Society on June 20, I was un- 
fortunately deprived of the opportunity I had hoped 
there to gain, of making a personal explanation 
which is important to me and which I beg to be 
allowed to make in NATURE. 
The conception of devising a camera wherewith 
photographs could be taken at the rate of 5000 a sec. 
occurred to me in consequence of some chance 
remarks made to me by an official of one of the great 
armament - producing companies in this country. 
The lion’s share of credit for the successful completion 
of the design of the camera, however, is due to my 
friend Mr. Horace B. Grylls, who became partner 
with me in this adventure in 1914; while both of us 
are indebted to my friend Prof. Boys, who, as all 
who know him will readily believe, gave us with 
both hands all the help and advice he had to give.” 
The interest which has lately been aroused by 
the exhibition of some of the films I took while the 
machine was still in Messrs. Thos. Cooke and Sons’ 
workshop in York—experimental films and far from 
perfect, I regret to say—calls for some such statement 
as I now, with great satisfaction, make here. 
WALTER HEAPE. 
Manor Lodge, Tunbridge Wells, 
June 21. 

Adsorption and Hemoglobin. 
Sir WiLt1Am Baytiss has pointed out, in NATURE 
for May 19, p. 666, that he is unable to find any 
account of experiments on the dissociation curve of 
hemoglobin at gas pressures considerably greater 
than that at which the hemoglobin is presumed to 
be saturated. He seems to imply that there is no 
proof that hemoglobin cannot take up more gas 
than is required by the theory that a chemical com- 
pound is formed, in which one molecule of O, or CO 
corresponds to one atom of iron. 
The point is important, not only as evidence on 
the relative merits of the chemical and adsorption 
theories, but also because experimental methods of 
determining the oxygen dissociation curve depend 
on the assumption that haemoglobin becomes com- 
pletely saturated, in contact with air, at the ordinary 
temperature of the laboratory. 
I have tried to test this question by shaking equal 
samples of the same blood (partly reduced) in the 
Barcroft differential apparatus, (1) with the bottle 
filled with air in the ordinary way, and (2) with the 
bottle filled with a mixture of air and CO, containing 
rather more than half an atmosphere of CO. 
It is known that hemoglobin takes up CO more 
than 200 times as readily as oxygen, so the effective 
gas pressures in the two cases were in the ratio of 
at least 500:1. If the hemoglobin takes up gas 
by adsorption, one would expect to find appreciably 
more CO taken up than oxygen. As a matter of 
fact, a little more CO was taken up, but only that 
quantity which is accounted for by the difference of 
solubility of CO and air in the liquids present (blood 
and dilute sodium carbonate solution). 
There was no evidence that the hemoglobin itself 
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