298 
NATURE 
[Aug. 14, 1873 
ward; and above all, the principle of selection should be 
other than that of competitive examination. The man 
with the peculiar talents and proved industry which are 
wanted for the post must be carefully sought for, and the 
place must be made for him, rather than the man manu- 
factured for the place. The managing body must be al- 
lowed perfect liberty either to found a new Fellowship for 
the particular man, or to refuse to fill up a vacant appoint- 
ment. All our Research Fellows will be, according to 
the German system, in extraordinary posts. From this it 
will follow that direct endowment of this kind, though 
the ultimate aim of our efforts, and by far the principal part 
of our scheme, is not the manner in which a beginning 
should be made. This form of endowment, so far as can at 
present be foreseen, must be comparatively exceptional, 
and therefore, when the right man is found, his position 
should be made one of handsome emolument, and it 
ought to be rendered impossible that he should be negli- 
gently passed over. 
The other ways in which research should be 
endowed may be regarded in the ultimate scheme 
as chiefly subsidiary to this, but in the order of 
time they must come first, The funds of the Colleges 
which are not wanted for teaching purposes, may at o:.ce 
be utilised for our object in an infinite number of indirect 
ways. They ought to be regarded as an abundant 
reservoir, from which may be continually drawn generous 
encouragement and ready help for those who happen to 
be carrying on some special investigation in any branch 
of Science. The Colleges should take the place which was 
occupied in England some century ago by those noble and 
wealthy patrons to whom Science, Art, and Literature all 
owe somuch. They should give in no grudging spirit, 
for they may be assured that an apparent waste in one 
direction will be amply compensated by the unlooked-for 
returns which they will reap in another. By throwing 
open their libraries, by -uilding museums and labora- 
tories, by supplying instruments or needful materials, by 
paying for laborious calculations or expensive publica- 
tions, as well as by subsidising any particular investiga- 
tion, they would breed up, so far as any artificial means 
can, that race of men from whom the selection must after- 
wards be made for their new Fellowships. To those 
who have had unfortunate experience of the management 
of college business, and of the sort of matters which come 
before a college meeting, such a reform as has been 
sketched out will doubtless appear as a visionary ideal ; 
yet it might be realised with very little trouble if the 
richest Colleges would transfer some of the attention 
which they now bestow upon ecclesiastical and educa- 
tional interests, to the cause of original research, and when 
realised, the result would be more nearly akin than the 
present, to that which the original statutes contem- 
plated, 
To answer the two other questions proposed need 
not take long, for an implicit reply to them has 
already been given. Fortunately, modern Science has 
taken such definite shape, and is pursued in such full 
publicity, that each branch has even now, at its 
head, certain acknowledged leaders, to whose judg- 
ments and recommendaticns in their special subjects, all 
deference is due, Until the Universities and the Colleges 
become sufficiently penetrated with the new scientific 
spirit, it will be natural that they should endow research 
under the guidance of the scientific societies, and of 
course it will be always necessary that they should be 
fully conscious of their responsibilities to the public for 
the appointments they confer upon the candidates, how- 
ever selected. The analogy of the Smithsonian Institu- 
tion will here again come in, for its assistance is never 
given in any case unless after a favourable report from a 
Commission of scientific men, who are experts in the 
particular matter submitted to them. 
With regard to the objection that the plan will 
inevitably tend to the foundation of a new store of 
sinecures, it is not incumbent to say more than that 
scientific posts, where the duty itself is of absorbing 
pleasure, are the least likely to degenerate in the way 
suggested, and that the in sinuation comes with an ill grace 
from those who are the present recipierts cf benefactions 
which they do so little to deserve. es 
ON LOSCHMIDT’S EXPERIMENTS ON DIF- 
FUSION IN RELATION TO THE KINETIC 
THEORY OF GASES 
HE kinetic theory asserts that a 
separate molecules, each moving with a velocity 
amounting, in the case of hydrogen, to 1,800 metres per 
second. This velocity, however, by no means determines 
the rate at which a group of molecules set at liberty in 
one part of a vessel full of the gas will make their way 
into other parts. In spite of the great velocity of the 
molecules, the direction of their course is so often altered 
and reversed by collision with other molecules, that the 
process of diffusion is comparatively a slow one, 
The first experiments from which a rough estimate of 
the rate of diffusion of one gas through another can be 
deduced are those of Graham.* Professor Loschmidt, of 
Vienna, has recentlyt+ made a series of most valuable 
and accurate experiments on the interdiffusion of gases 
in a vertical tube, from which he has deduced the co- 
efficient of diffusion of ten pairs of gases. These results 
I consider to be the most valuable hitherto obtained as 
data for the construction of a molecular theory of gases. 
There are two other kinds of diffusion capable of experi- 
mental investigation, and from which the same data may 
be derived, but in both cases the experimental methods 
are exposed to much greater risk of error than in the 
case of diffusion. The first of these is the diffusion 
of momentum, or the lateral communication of sen- 
sible motion from one stratum of a gas to another, 
This is the explanation, on the kinetic theory, of 
the viscosity or internal friction of gases. The inves- 
tigation of the viscosity of gases requires experiments of 
great delicacy, and involving very considerable correc- 
tions before the true coefficient of viscosity is obtained, 
Thus the numbers obtained by myself in 1865 are 
nearly double of those calculated by Prof. Stokes from 
the experiments of Baily on pendulums, but not much 
more than half those deduced by O. E. Meyer from his 
own experiments. The other kind of diffusion is that of 
the energy of agitation of the molecules. This is called 
the conduction of heat. The experimental investigation 
* Brande's Fournal for 1829, pt. ii. “On the Mobility of Gases,” 
Phil. Trans. 1863, 9» pt. 1, DP. 74, waty 
t Sitzb, dik. Akad. d. Wissench, 10 Miirz, 1870. 
gas consists of 
