

Aug. 3 1871 | 
NATURE 
269 

periodic time in passing any particular point, and gave a choice 
of five different periods for the revolution of this meteoric stream 
round the sun, any one of which would satisfy his statistical result. 
He further concluded that the line of nodes, that is to say, the 
line in which the plane of the meteoric belt cuts the plane of the 
Farth’s orbit, has a progressive sidereal motion of about 52”°4 
per annum. Here, then, was a splendid problem for the physical 
astronomer ; and, happily, one well qualified for the task, took it 
up. Adams, by the application of a beautiful method invented 
by Gauss, found that of the five periods allowed by Newton just 
one permitted the motion of the line of nodes to be explained by 
the disturbing influence of Jupiter, Saturn, and other planets. 
The period chosen on these grounds is 33} years. ‘The investi- 
gation showed further that the form of the orbit is a long ellipse, 
giving for shortest distance from the Sun 145 million kilometres, 
and for longest distance 2,895 million kilometres. Adams also 
worked out the longitude of the perihelion and the inclination of 
the orbit’s plane of the ecliptic. The orbit which he thus found 
agreed so closely with that of Tempel’s Comet I. 1866 that he 
was able to identify the comet and the meteoric belt.“ The 
same conclusion had been pointed out a few weeks earlier by 
Schiaparelli, from calculations by himself on data supplied by 
direct observations on the meteors, and independently by Peters 
from calculations by Leverrier on the same foundation. 
therefore thoroughly established that Temple’s Comet I. 1866 
consists of an elliptic train of minute planets, of which a few 
thousands or millions fall to the earth annually about the 14th of 
November, when we cross their track. We have probably not 
yet passed through the very nucleus or densest part; but thirteen 
times, in Octobers and Novembers, from October 13, A.D. 902 
to November 14, 1866 inclusive (this last time having been cor- 
rectly predicted by Prof. Newton), we have passed through a 
part of the belt greatly denser than the average. 
part of the train, when near enough to us, is visible as the head 
of the comet. This astounding result, taken along with Huggins’s 
spectroscopic observations on the light of the heads and tails of 
comets, confirms most strikingly Tait’s theory of comets, to which 
T have already referred ; according to which the comet, a group 
of meteoric stones, is self-luminous in its nucleus, on account of 
collisions among its constituents, while its ‘‘tail” is merely a 
portion of the less dense part of the train illuminated by sunlight, 
and visible or invisible to us according to circumstances, not only 
of density, degree of illumination, and nearness, but also of tactic 
arrangement, as of a flock of birds or the edge of a cloud of 
tobabco smoke! What prodigious difficulties are to be explained, 
you may judge from two or three sentences which I shall read 
from Herschel’s Astronomy, and from the fact that even Schiapa- 
relli seems still to believe in the repulsion. ‘‘ There is, beyond 
question, some profound secret and mystery of nature con- 
cerned in the phenomenon of their tails. Perhaps it is not too 
much to hope that future observation borrowing every 
aid from rational speculation, grounded on the progress of 
physical science generally (especially those branches of it which 
relate to the etherial or imponderable elements), may enable us 
ere long to penetrate this mystery, and to declare whether it is 
really #zatter in the ordinary anticipation of the term which is 
projected from their heads with such extraordinary velocity, and 
if not zmzfelled, at least directed, in its course, by reference to the 
Sun, as its point of avoidance.” + 
“*Tn no respect is the question as to the materiality of the tail 
more forcibly pressed on us for consideration than in that of the 
enormous sweep which it makes round the sun 77 ferihelio, in 
* Signor Schiaparelli, Direc'or of the Observatory of Milan, who, in a 
letter dated 51st December, 1866, pointed out that the elem nts of the orbit 
of the August Meteors, calcu'ated froin the observed position of their radiant 
point on the supposition of the orbit being a very elongated ellipse agreed 
very closely with those of the orbit of Comet II 1£62, calculated by Dr. 
Oppolzer. In the same letter Schiaparelli gives clements of the orbit of the 
November meteors, but thes: were not sufficiently accurate to enable him to 
identify the orbit with that of any known comet. On the 21st January, 
1867, M. Leverrier gave move accurate elements of the orbit of the Novem- 
ber Meteors, and in the “ Astronomische Nachrichten” of January 9, Mr. C. 
F. W. Peters, of Altona, pointed out that these elements closely agreed with 
those of Tempe.’s Comet (I. 1865 , ca'culated by Dr. Oppol zer, and on Feb. 2, 
Schiaparelli having recalculated the elements of the orbi: of tre meteors 
himself noticed the sam+ agreement. Adams arrived quite independently 
at the conclu-ion that the orbit of 3} years period is the one which must be 
chosen out of the five indicated by Prof. Newton. His calculations were 
suffic'ently advanced before the letters referred to appeared, to show that the 
other fuur orbits offered by Newtoa were inadmissible. But the calculations 
to be gone through to find the secular mo ion of the node in such an elongated 
orbit as that of the meteors, were necessarily very long, so that they were 
not completed till about March 1867. They were communicated in that 
month to the Cambridge Philosophical Society, and in the month following to 
the Astronomical Society. + Herschel’s Astronomy, § 599. 
It is | 
The densest | 
| 

the manner of a straight and rigid rod, 2 defiance of the law of 
gravitation, nay, even of the recetved laws of motion.” * 
** The projection of this ray . . . to so enormous a length, in 
a single day conveys an impression of the intensity of the forces 
acting to produce such a velocity of material transfer through 
space such as no other natural phenomenon is capable of ex- 
citing. Itis clear that 7f we have to deal here with matter, such 
as we conceive tt, viz., possessing inertia—at all, it must be under 
the dominion of forces incomparably more energetic than gravi- 
tation, and quite of a different nature.” + ; 
Think now of the admirable simplicity with which Tait’s beau- 
tiful ‘‘sea-bird analogy,” as it has been called, can explain all 
these phenomena. 
The essence of science, as is well illustrated by astronomy and 
cosmical physics, consists in inferring antecedent conditions, and 
anticipating future evolutions, from phenomena which have 
actually come under observation. In biology, the difficulties of 
successfully acting up to this ideal are prodigious. The earnest 
naturalists of the present day are, however, not appalled or 
paralysed by them, and are struggling boldly and laboriously 
to pass out of the mere ‘* Natural History stage” of their study, 
and bring Zoology within the range of Natural Philosophy. A 
very ancient speculation, still clung to by many naturalists (so 
much so that I have a choice of modern terms to quote in ex- 
pressing it) supposes that, under meteorological conditions very 
different from the présent, dead matter may have run together 
or crystallised or fermented into ‘‘germs of life,” or ‘‘ organic 
cells,” or ‘* protoplasm.” But science brings a vast mass of 
inductive evidence against this hypothesis of spontaneous gene- 
ration, as you have heard from my predecessor in the Pre:-i- 
dential chair. Careful enough scrutiny has, in every case up to 
the present day, discovered life as antecedent to life. Dead 
matter cannot become living without coming unaer the influence 
of matter previously alive. This seems to me as sure a teaching 
of science as the law of gravitation. I utterly repudiate, as 
opposed to all philosophical uniformitarianism, the assumption of 
“different meteorological condition”’—that is to say, somewhat 
different vicissitudes of temperature, pressure, moisture, gaseous 
atmosphere—to produce or to permit that to take place by force 
or motion of dead matter alone, which is a direct contravention 
of what seems to us biological law. I am prepared for the 
answer, ‘‘our code of biological law is an expression of our 
ignorance as well of our knowledge.” And I say yes: search 
for spontaneous generation out of inorganic materials ; let any 
one not satisfied with the purely negative testimony of which we 
have now so much against it, throw himself into the inquiry. 
Such mvestigations as those of Pasteur, Pouchet, and Bastian 
are among the most interesting and momentous in the whole 
range of Natural History, and their results, whether positive 
or negative, must richly reward the most careful and laborious 
experimenting. I confess to being deeply impressed by the 
evidence put before us by Professor Huxley, and I am ready to 
adopt, as an article of scientific faith, true through all space and 
through all time, that life proceeds from life, and from nothing 
but life. 
How, then, did life originate on the Earth? Tracing the 
physical history of the Earth backwards, on strict dynamical 
principles, we are brought to a red-hot melted globe on which 
no life could exis Hence when the Earth was first fit for life, 
there was no living thing on it. There were rocks solid and 
disintegrated, water, a'r all round, warmed and illuminated by 
a brilliant Sun, ready to become a garden. Did grass and trees 
and flowers spring into existence, in all the fulness of ripe 
beauty, by a fiat of Creative power? or did vegetation, growing 
up from seed sown, spread and multiply over the whole Earth ? 
Science is bound, by the everlasting law of honour, to face fear- 
lessly every problem which can fairly be presented to it. Ifa 
probable solution, consistent with the ordinary course of nature, 
can be found, we must not invoke an abnormal act of Creative 
Power. When a lava stream flows down the sides of Vesuvius 
or Etna it quickly cools and becomes solid ; and alter a few 
weeks or years it teems with vegetable and animal life, which 
for it originated by the transport of seed and ova and by the 
migration of individual living creatures When a volcanic island 
springs up from the sea, and after a few years is found clothed 
with vegetation, we do not hesitate to assume that seed has been 
wafted to it through the air, or floated to it on rafts. Is it 
not possible, and if possible, is it not probable, that the begiv- 
ning of vegetable life on the earth is to be similarly explained ? 

* Herschel’s Astronomy, § 599. + Jbid., roth Edition, § 589. 
