494 
NATURE 
[Oct. 9, 1873 
on the march from the Indus to the Tigris, by H. W. Bellew, 
C.S.I,, Surgeon to the Bengal Staff Corps. ‘‘The Rod in 
India ;” being hints how to obtain sport, with remarks on the 
natural history of ‘fish, otters, &c., and illustrations of fish and 
tackle, by H. S. Thomas, F.L.S., F.Z.S. A third and enlarged 
edition of the ‘*Celt, the Roman, and the Saxon,” a history 
of the early inhabitants of Britain, down to the conyersion of the 
Anglo Saxons to Christianity, illustrated by the ancient remains 
brought to light by recent research, by Thomas Wright, M.A., 
F.S.A. : 
A DEPUTATION from the Trades’ Guild of Learning waited 
on Tuesday afternoon on a Sub-Committee of the London School 
Board, at the invitation of the School-Management Committee, 
in order to urge upon the Board the adoption of systematic 
training in mechanics, &c., with the object of adapting the scien- 
tific instruction, provided or contemplated in the Board schools, 
to the future employments of the children. A memorial to the 
same effect has been presented to the Board, and is now under 
their consideration, in favour of the elementary teaching of ap- 
plied science and art in the schools, in such a manner as to lay 
the foundation of a connected system of technical education. 
News has been received of the death at Quito, Ecuador, in 
June last, of Dr, William Jameson, an eminent naturalist, who 
resided for many years in Quito as a professor of chemistry and 
botany in the University. His contributions, both in zoology 
and botany, to public institutions in America and Europe have 
been very extensive, 
Dr. DAviD Moore reprints from the ‘‘ Proceedings of the 
Royal Irish Academy ” a complete Muscology of Ireland, under 
the title ‘‘ Synopsis of all the Mosses known to inhabit Ireland 
up to the present time.” 
THE additions to the Zoological Society’s Gardens during the 
past week include two Black-headed Parrots (Caica melano- 
cephala) from Demerara, presented by Judge Lovesy ; a Brown 
Bear (Ursus arctos), European, presented by Mr. M. B. Wilson ; 
a Thicknee (Oedicnemus crepitans), British, presented by Mr. 
Patey ; a Lesser Black- backed Gull (Zarus fuscus), British, pre- 
sented by Mr. C. W.\Wood; a Hairy Armadillo (Dasypus 
villosus), from River Plate; a Burrowing Owl (Pholeoptynx 
cunicularia), from the same place, deposited ; a Wattled Crane 
(Grus carunculata), from Africa, and two Bataleur Eagles 
(Helotarsus ecaudatus), 
THE BRITISH ASSOCIATION 
SECTIONAL PROCEEDINGS 
SECTION A,—MATHEMATICS AND Puysics 
On Etherial Friction, by Prof. Balfour Stewart, LL.D., F.R.S. 
Professor J. C. Maxwell has made a series of experiments on 
the friction of gases. In these experiments a horizontal disc 
was made to oscillate in an imperfect vacuum near a similar disc 
at rest, and it was found that the motion of the oscillating disc 
was carried away by the residual gas of the vacuum ata rate 
depending on the chemical character of the gas, and depending 
also upon its temperature, but nevertheless independent of its 
density. 
_ While the temperature of the arrangement remained constant, 
it was found by Prof. Maxwell that this fluid friction was rather 
greater for atmospheric air than for carbonic acid, while for 
hydrogen it was, I think, about half as great as for air. 
On the other hand, when the temperature was made to vary 
the result was found to be proportional to the absolute tem- 
perature, 
These experiments do not show that there is no such thing as 
etherial friction, that is to say, friction from something which 
fills all space, and is independent of air ; but we may argue from 
them that such an etherial friction must either have been nearly 
insensible in these experiments, or it must, as well as the friction 
from the gas, have varied with the absolute temperature, in 
which case the two frictions would not be separated from one 
another by the method of the experiment. ‘ 
Prof. Tait and myself have made some experiments upon the 
heating of a disc by rapid rotation in ‘vacuo. In these experi- 
ments we found a mere surface heating due to air which varied 
not only with the quality, but also with the quantity of the residual 
gas; and we also found a surface, effect (more deeply seated 
however than the former), which appeared to be a residual 
effect, and which it is possible may be due to etherial friction. 
We made no experiments at varying temperatures, but we made 
use of various residual gases, and we found that the heating 
effect for carbonic acid was perhaps a trifle less than for air, 
while that for hydrogen appeared to be about four times less than 
that for air. Now comparing Prof. Maxwell’s experiments with 
ours, we have in the former a stoppage of motion which is rather 
less for carbonic acid than for air, and about half as large for 
hydrogen as for air, In the latter again we have a heating effect 
rather less for carbonic acid than for air, and only about one- 
fourth as large for hydrogen as for air. Thus it appears that the - 
stopping effect of hydrogen in Prof Maxwell’s experiments is 
relatively greater in comparison with air than is its heating 
effects in our experiments, when compared with that of air. 
The effects of these various gases would bear to one another 
more nearly the same proportion in both experiments, if we 
might suppose that in Prof, Maxwell’s experiments there was 
mixed up with gaseous friction a very sensible etherial friction ; 
but in that case it would be necessary to suppose that the etherial 
friction was proportional to the absolute temperature, 
During the meeting of the British Association at Edinburgh, 
I brought before this section reasons for imagining that if we 
have a body in visible motion in an enclosure of constant tem- 
perature, the visible motion of the body will gradually be 
changed into heat. The nature of the argument was such as to 
render it probable (although not absolutely certain) that in such 
a case the rapidity of conversion will be greater the higher the 
temperature of the enclosure, 
Iwill now refer to some experiments by Prof. Tait which 
formed the subject of the last Rede Lecture. These experi- 
ments were suggested to Prof, Tait by an hypothesis derived 
from the theory of the dissipation of energy which led him to 
think that the resistance of a substance to the conduction of 
electricity, and also of heat, would be found proportional to the 
absolute temperature. Mattiessen and Von Bose in the case of 
electricity, and Principal Forbes in the case of heat, had already 
proved that asa matter of fact the law was not very different 
from that imagined by Prof. Tait. The result of these experi- 
ments has been to confirm the truth of this law. = 
The following considerations also connected with the dissipation 
of energy point to the same conclusion, Perhaps we may 
the etherial medium as that medium whose office it is to degrade 
all directed motion, and ultimately convert it into universally 
diffused heat, and in virtue of which all the visible differential 
motion of the universe will ultimately be destroyed by some pro- 
cess analogous to friction, 4 
Now in order to imagine the way in which either may possibly 
act in bringing about this result, let us imagine some familiar 
instance of directed motion, as for instance a railway train in 
motion. The train, let us suppose, and the air in it, are both in 
rapid motion, while the air outside is at rest. Now as the train 
proceeds, suppose that a series of cannons loaded with blank 
cartridges are fired towards the train. A series of violent 
sounds will go in at the one window, and out at the other of 
each carriage. Each sound will push some air from the stratum 
of air at rest into the carriage on the one side, and it will push 
some air from the carriage into the stratum at rest on the other 
side. Now in this operation it would seem that part of the 
visible motion of the train must be taken from it. To make another 
comparison, it is as if a series of individuals were jumping into 
the train at the one side, and out of it at the other, the result 
being that each carries away so much of the motion of the train, 
and therefore renders it difficult for the engine to drive the train. 
Each individual comes to the ground with an immense forward 
impetus, and rubs along the ground till this is lost ; in fact, he’ 
carries with him so much motion of the train, and converts it 
into heat by friction against the ground. 
Now something similar to this must happen to a substance in 
visible motion in an enclosure of constant temperature. The 
rays of light and heat will play very much the same part as the 
waves of sound, or as the crowd of people in the above illus- 
tration, at least if we except those which fall perpendicularly 
