April 7, 1870 | 
NATURE 
583 
conversely that every possible free motion about its centre of 
gravity of every such solid admits of being so represented. 
To revert for an instant to the general question of the represen- 
sentative rolling ellipsoid, I think it must be admitted that the ad- 
dition of the time element to the theory and the substitution 
of a second fixed plane in lieu of a fixed centre, considerably 
enhance the value and give an unexpected roundness and com- 
pleteness to Poinsot’s image of the free motion of rotation of 
a rigid body, of which so much and not altogether unde- 
servedly has been made. From an idea or shadow Poinsot’s 
representation has now become a corporeal fact and reality, as 
if, so to say, Ixion’s cloud, in the moment of fruition, had sub- 
stantified into a living Juno. I heard the late Professor Donkin, 
of revered and ever-to-be-cherished memory, state that when as 
a referee of the Royal Society he first took in hand my paper on 
rotation, he did so with a conviction that all had already been 
said that could be said on the subject, and that it was a closed 
question; but that when he laid down the memoir he saw reason 
to change his opinion. JI owe my thanks to M. Radau and the 
editors of the Annals of the Ecole Normale Supérieure for having 
been at the pains to disentomb the little-known conclusions 
therein contained from their honourable place of sepulture in the 
Philosophical Transactions. J. J. SYLVESTER 
K House, Woolwich Common, April 2 
The Principle of the Conservation of Force and 
Mr. Mill’s System of Logic 
WILL you permit me briefly to point out, what has not, as far 
as I am aware, been yet noticed—the very important modifica- 
tions of the logical theory of induction resulting from the con- 
sideration in reference thereto of the physical theory of the 
correlation of forces ? 
As I believe the subject is now more ripe for discussion than 
it was when, some dozen years ago, I first began to work out 
the bearings of the higher results of physical research on the 
general theory of causation, logical, and metaphysical; the 
following questions which, in the course of a correspondence on 
this subject, I submitted to Mr. Mill so long ago as 1863, may, 
perhaps, contain suggestions of thought not unwelcome to some 
students of NATURE. 
‘< How then,” I wrote, ‘‘do our new views of force affect the 
established theory of causation? Now I would rather, if you 
will allow me, submit the whole subject interrogatively to you, 
than give dogmatically my own thoughts. And, more particu- 
larly, allow me to submit to you these two questions—rst, 
Whether the physical theory of transformation (and identity) 
does not necessitate all such logical changes of expression, at 
least, as may be implied in the abolition of the conceptions of 
‘*permanent causes,” and of ‘‘kinds,” as real and absolute 
existences ? And, 2ndly, whether—‘“if, as I have endeavoured to 
show, the inductive facts on which are based the principles of 
conservation and correlation lead to such a more general prin- 
ciple as may be thus expressed, every existence has a deter- 
mined and determining co-existence,—whether, I say, ‘‘ we are 
not justified in enunciating such a principle as the complement 
of that fundamental axiom of our present logic, ‘every effect has 
a cause’ ?” 
I believe I am at liberty to say that, though affirmative 
answers to these questions would necessitate very important 
changes in the ‘‘system of logic, inductive and ratiocinative,” 
Mr. Mill, as to the first, admitted the necessity of certain 
changes of expression, at least, and generously encouraged me 
in the prosecution of the researches indicated by the second 
question. 
Of the results of these researches I shall here only say that, as 
the axiom, “every effect has a cause,” is the foundation of a logic 
which must be distinguished asa /ogic of sequence, the new axiom 
above stated may be shown to be the basis of a Jogic of co- 
existence, of which Geometry appears as an example. But as to 
this, as to the conception of force implied in this idea of co- 
existence, and as to the bearing of this new conception of force 
on the speculations with regard to space of a fourth dimension, 
perhaps I may have another opportunity of addressing you. 
J. S. STUART GLENNIE 
Athenzeum Club, March 30 
Dust and Germs of Life 
Pror. TYNDALL’s exceedingly interesting article in No. 20 
of NATURE seems to me to leave unexplained a fact very 
familiar to naturalists. It is well known that collections of 
natural history,;sayfa Herbarium or an Entomological cabinet, 
will, if left undisturbed for a number of years, and unpoisoned, 
become infested with animal life, chiefly Acari and larve of 
Coleoptera; and that the surest way of preventing such 
attacks is thorough ventilation. Now if the floating matter 
in the air settles so readily after only a few days’ stillness, as 
Prof. Tyndall’s experiments seem to indicate, and does not even 
enter into an uncorked flask, it is out of the question that it can 
penetrate through the keyholes or chinks of our cabinets. Setting 
aside the theory of spontaneous generation, we are then forced 
to the conclusion that this life must arise from germs already 
existing in the specimens when they are preserved, or in the 
very limited amount of atmosphere originally confined in the 
cabinet. Is either of these explanations tenable ? A strong argu- 
ment against the former alternative seems presented by the fact 
that, as far as lam aware, the same species of Acarus infests plants 
in a Herbarium brought from the most widely diverse localities, 
an inland meadow or the seashore, the plains of England or the 
Alps of Switzerland. Can any of your physiological readers 
throw light on this subject ? BS Ta Se 
Catkins of the Hazel 
WHILE looking at some hazel bushes to-day, I noticed that 
where the red tuft of stigmas was protruded, the male catkins 
adjacent on the same twig were immature ; while, on the other 
hand the stigmas had fallen, and the fruit was already swelling, 
where the scales of the male flowers were open to show the 
stamens. 
A week or two back (in another locality) I could not find a 
single female catkin which had not lost its stigmas; while 
nearly all the male catkins had opened, and many had shed their 
pollen. 
Is this always the case with the hazel? If so, it would bea 
striking illustration of Darwin’s aphorism, ‘‘ Nature abhors per- 
petual self-fertilisation.” 
I ought to add, that my observations are not confirmed by the 
illustrations in the books to which I have access, namely, Balfour’s 
**Class Book,” Lindley’s “School Botany,” and Lemaout and 
Decaisnes’ “ Traité de Botanique.” In all these, a female catkin 
with its tuft of stigmas is represented on the same twig as a 
bunch of fully developed male catkins. 
Will some one of greater experience inform me if I am in 
error as to the above facts ? Marcus M. Hartoe 
University College, London, March 24 
ANCIENT BRITISH LONG BARROWS 
II, 
HE chambered long barrows of North Wilts, Somer- 
set, and Gloucestershire differ, as a rule, but slightly 
in external form from the simple or unchambered long 
barrows of South Wilts and Dorset. They are, however, 
generally of somewhat smaller dimensions, being from 
about 120 to 200 feet in length and from 30 to 60 feet in 
breadth. The side ditches characteristic of the uncham- 
bered barrows are seldom to be met with, but the margin 
of the grave-mound is, or rather was, usually defined by a 
low wall, built of loose tile-shaped fragments of oolitic 
stone. In some cases, as at West Kennet (see fig. 1), 
there is good evidence that the mound was originally 
surrounded by a series of obelisks of sarsen stone, the 
intervals being filled up with the usual dry walling just 
described. Sometimes, too, large monoliths or triliths 
are found at the broad end of the tumulus. As regards 
orientation, or position in reference to the points of the 
compass, the direction of east and west commonly ob- 
served in the simple barrows prevails in four out of five 
cases with the chambered barrows ; and as in the former 
class of monument the interments were at the eastern 
end, which is also the higher and broader, so likewise do 
we find that the stone chambers or cists occupy the same 
position in the chambered barrows. 
In internal structure the chambered barrows exhibit 
many varieties, but three principal types are recognised 
by Dr, Thurnam, viz.—(1) those in which the chamber 
