458 
slower motion and to their generally entering the shadow 
more obliquely; their inclinations and nodes were less 
accurately known, while it was well known that the 
motions of the outer satellites differed in a very irregular 
manner from Cassini’s tables by amounts much larger 
than that dealt with in the case of the first satellite. 
The deviation in question was neither a function of the 
anomaly of Jupiter nor of that of the earth, nor of the 
configuration of the satellites, but solely of the distance 
from the earth. Writing to Colbert shortly afterwards, 
Huygens calls the discovery a most important one, in 
the confirmation of which the Royal Observatory would 
be worthily employed, and he adds that he was all the 
more pleased, as he had himself already, by means of 
this hypothesis, demonstrated the laws of the double 
refraction in Iceland spar. To Roemer he wrote that 
Cassini’s objection did not trouble him much, as long as 
there were not better ephemerides of the outer satellites 
available. He doubted that observations of the surface- 
markings of Jupiter would be of any use in this inquiry, 
as they could not be accurate enough; but this Roemer 
did not acknowledge, since the time of passage of a 
spot across the central meridian could be fixed within 
two minutes. In a subsequent letter and in a com- 
munication to the Academy (which does not seem to 
have been printed before), Roemer proudly gives observ- 
ations of a spot of September and December 1677, the 
comparison of which with an assumed value of the 
period of rotation seemed to exhibit the phenomenon 
beautifully. Of much greater interest is a remark made 
by Roemer in a letter dated December 30, 1677, in which 
he points out that the motion of the earth must affect 
the apparent direction of the path of light! In Cartesian 
language, he expresses this by saying that the circular 
motion of the terrestrial vortex must produce a curvature 
of the path, and he ingeniously suggests that the amount 
of this deflection might be determined by selecting two 
stars in the zodiac, nearly opposite each other, and ob- 
serving their angular distance apart, first when one was 
at its heliacal rising, and again four or five months later 
when the other approached its heliacal setting. The 
difference would be four times the amount of the de- 
flection, or, as we should say, four times the constant of 
aberration. It is very remarkable that Picard, Roemer’s 
teacher and friend, should have discovered the changes 
in the place of the pole-star due to aberration (and also 
those due to nutation, though not the laws which regulate 
either—see his “‘ Voyage d’Uranibourg,” article viii.), 
while Roemer logically concluded from his discovery of 
the velocity of light that there ought to be aberration of 
light. But it was reserved for Bradley to publish both the 
Jaws and the theory of aberration. These facts become still 
more curious when we reflect that, but for the unfortunate 
destruction by fire of almost all Roemer’s observations— 
which had been made with instruments constructed on 
novel principles not adopted elsewhere till much later, 
the foundation of modern astronomy might have been 
built on them and not on Bradley’s observations. It 
was indeed unfortunate that Roemer published so very 
little about his scientific labours, and it is therefore par- 
ticularly interesting to get a slight insight into them 
through his correspondence with Huygens. 
NO. 1559, VOL. 60] 
NATURE 
[SEPTEMBER 14, 1899 
Among other matters dealt with in this volume we 
may mention the controversy on the theory of the centre 
of oscillation between Huygens and Abbé de Catelan, a 
man whose aim in life seems to have been to object to 
every new mathematical publication and to exhibit his 
inability to grasp any new theory. In Vol. i. of Huygens’ 
“ Opera varia,” the papers written by the two opponents, 
as well as by Jacques Bernouilli, who took Huygens’ 
part, have already been printed side by side ; but it is 
interesting to see from the correspondence that Catelan’s 
attack was slyly inserted in the Amsterdam reprint of 
the Journal des Scavans, although it had not appeared in 
the original Paris edition. 
The volume contains as frontispiece a plate reproduc- 
ing a fine medallion of Huygens from 1679, and another 
showing a medal apparently struck in his honour in the 
same year. It is announced that his unpublished works 
are to appear in the volumes following immediately after 
those devoted to his correspondence. 
J. L. E. DREYER. 
METAPHYSICS OF BIOLOGY. 
The Living Organism: an Introduction to the Problens 
of Biology. By Alfred Earl, M.A. Pp. xiii+ 271. 
(London : Macmillan and Co., Ltd., 1898.) 
HE observer of the more recent phases of biological 
thought will not need to be told that during the 
last few years a reaction has been setting in, both in 
England and abroad, against any so-called mechanical 
theories of the origin and development of living things, 
and against any hypothesis which seeks in the facts of 
chemistry and physics for an ultimate explanation of the 
phenomena of life; and those who have had the oppor- 
tunity of a more intimate acquaintance with this new 
philosophical development will know that the “neo- 
vitalist”” adopts, as the basis of his scientific beliefs, an 
ontology which states that it is not true that the hierarchy 
of the natural sciences presents us with a material universe 
of which the separate parts studied by the several sciences 
can all be ultimately expressed in terms of one of them, 
biology in fact being a special case of chemistry, this of 
physics and so on; but that on the contrary every 
science deals, not with a part, but with the whole of the 
material universe, all the facts of which come under its 
survey, and asa particular manner of looking at which 
it is to be regarded. On this view, therefore, it is as 
useless ever to expect a physical explanation of the 
chemical atom as it is futile to hope that organic meta- 
bolism may after all turn out to be merely a specially 
complex chemical reaction: each science has what is, 
for itself, an ultimate fact, in terms of which it seeks to 
express the whole of nature, but which has nothing in 
common with the ultimate fact of any other science 
whatever. This ultimate fact is, for the vitalistic bio- 
logist, the living organism, and when pressed for an 
account of how the inanimate world is included in his 
science, he replies by a reference to the environment, 
which, we are told, is to be regarded as being made by 
and for the organism itself. 
Now it may be that the ontology which includes, with 
Kant, all phenomena in but a single category is obsolete, 
