512 
NA TORE. 
[ Sept. 24, 1885 
were full of their own measurements and calculations, sketch- 
maps and farm-drawings, severely accurate and logically classi- 
fied, to be then compared with those recorded in the books. 
What teachers fail to keep in mind isthis: that learning is not 
knowledge ; but as Lessing says: Learning is only our know- 
ledge of the experience of others ; knowledge is our own. No 
man really comprehends what he himself has not created. 
Therefore we know nothing of the universe until we take 
it to pieces for inspection, and rebuild it for our under- 
standing. Nor can one man do this for another; each must 
do it for himself; and all that one can do to help another 
is to show him how he himself has morsellated and recomposed 
his small particular share of concrete nature, and inspire him 
with those vague but hopeful suggestions of ideas which we call 
learning, but which are not science. 
My third proposition was that an expert in practical science 
can command the respect and confidence of his professional 
fellows, and through their free suffrages buld up his own repu- 
tation in the learned and business worlds, only in exact propor- 
tion to the amount of good dead-work to which he voluntarily 
subjects himself. For, although the most of it is necessarily 
done in secrecy ana silence, enough of it leaks out to testify to 
his honest and diligent self-cultivation ; and enough of it must 
show in the shape of scientific wisdom to make self-evident the 
fact that he is neither a tyro nor a charlatan. More than once I 
have heard the merry jest of the Australasian judge quoted with 
sinister application to experts in science. When a young col- 
league, just arrived from England, asked him for advice, he 
answered : Pronounce your decisions, but beware of stating your 
reasons for them. Many an ephemeral reputation for science 
has been begot by this shrewd policy ; but the best policy to 
wear well is honesty ; and honesty in trade means selling what 
is genuine, well-made, and durable ; and honesty in science 
means, first, facts well proved, and then conclusions slowly and 
painfully deduced from facts well proved, in sufficient number 
and order of arrangement to exhaust alike the subject and the 
observer. Reap your field so thoroughly that gleaners must 
despair. Fortify your position, that your most experienced rival 
can find no point of attack. Lay your plans with such a super- 
fluity of patient carefulness that fate itself can invent no serious 
emergency. Demonstrate your theory so utterly and evidently 
that it shall require no defender but itself. Die for your work, 
that your work may live for ever. Forget yourself, and your 
work will make you famous. Enslave yourself to it, and it will 
plant your feet upon the necks of kings, and your mere Yes or 
No will become a law to multitudes. This is what the dead- 
work of science, when well done, does for the expert in science. 
My fourth proposition—that only the habitual performance of 
dead-work can preserve the scientific intellect in pristine vigour, 
and prevent it from becoming stiffened with prejudices, inapt to 
receive fresh truth, and forgetful of knowledge already won— 
hardly needs discussion. Human muscles become atrophied by 
disuse. Men’s fortunes shrink and evaporate by mere invest- 
ment. I pray you to imagine what I wish to say, for it all 
amounts to this—that the grass will surely grow over a deserted 
footpath. Let me hurry to the close of this address, which I 
have found too serious a duty for my liking, and perhaps you 
also have found it too personal a preachment for yours. One 
more suggestion, then, and I have done. 
My fifth proposition was that the wearied and exhausted 
intellect will wisely seek refreshment in dead-work. 
The physiology of the brain is now sufficiently well under- 
stood to permit physicians to prescribe with some assurance for 
its many ills, and to regulate its restoration to a normal state of 
health. Its tissues reproduce themselves throughout life if no 
extraordinary oyer-balance of decay takes place, if there be no 
excessive and too long-continued waste. For the majority of 
mankind, nature provides for the adjustment between consump- 
tion and reproduction of brain matter, by the alternations of day 
and night, noise and silence, society and solitude; and also by 
the substitution of the play of fancy in dreams, for the work of 
the judgment and the will in waking hours. We follow the 
lead of nature when we seek amusement as a remedy for care. 
We bring into activity a rested portion of the brain, to permit 
the wearied parts of it to restore themselves unhindered. 
In Section A Prof. Newton, of Yale, read a paper upon 
“The Effect of Small Bodies passing near a Planet upon the 
Planet’s Velocity.” 
The former researches of Prof. Newton upon meteors are 
recognised among astronomers as our principal source of 
knowledge about the character, distribution, and motion of 
these minute bodies with which the solar system is filled, 
especially those which strike our atmosphere and are burned up 
as meteors. The possible effect of these upon the rotation of 
the earth, and the revolution of the earth and moon in their 
orbits, has been subjected to elaborate investigation at the hands 
of several mathematical astronomers. The recent publications 
of Mr. Denning, of Bristol, claiming the fixity of long-continuing 
radiant points of meteor streams, have raised the question of the 
existence of broad streams of meteoroids moving swiftly through 
stellar space outside of solar attraction ; and any new investiga- 
tion bearing upon any of these points is more than usually 
timely. In this paper Prof. Newton has discussed the effect 
upon the earth’s motion of those bodies which do not pass near 
enough to the earth to be drawn into its atmosphere, but still 
near enough to be drawn out of their course, and swung for a 
time in hyperbolic orbits around it. He began by saying that 
the results of the investigation might perhaps be considered 
negative as far as measurable quantities in the solar system are 
concerned, but that they had a mathematical interest, and might 
possibly have a bearing upon somewhat similar questions in 
molecular physics, like the kinetic theory of gases. The mathe- 
matician and astronomer must be referred to the paper itself, 
and the results of popular interest may be briefly summarised as 
follows :—Considering, first, the case of a cylindrical stream of 
small bodies evenly distributed, and all moving in the same direc- 
tion with a common velocity past the earth supposed to be in the 
axis of the cylinder, it is shown that they will communicate to the 
earth in each unit of time a velocity along the axis: (1) that is 
proportional to the density of the group ; (2) that decreases as the 
velocity increases nearly inversely as the square of the velocity ; 
(3) that increases as the logarithm of the radius of the cylinder, 
the radius being measured by a unit differing from the earth’s 
radius by a small quantity, which is a function of the velocity. 
Second, in the case of a widely-extended group of small bodies 
evenly distributed in space, and having speeds all equal, but 
directed towards points evenly distributed over the celestial 
sphere with the earth moving ina right line through them, it is 
shown that, for those which do not strike the earth, but only 
affect it by their attraction, the effect will be an exceedingly 
minute acceleration of the earth’s motion, if the latter zs ess than 
that of the bodies, even though the group is infinite in extent. If 
the earth’s velocity zs greater than that of the bodies, their total 
effect will consist of two parts: a very minute retardation of the 
earth’s motion, depending in amount upon the absolute velocity 
cf the bodies; and another retardation depending upon the 
assumed extent ofthe group. In cenclusion, the effect of bodies 
striking the earth or moon is manifold greater than that of those 
only passing near ; and since it has before been shown that any 
admissible magnitude of meteroids would make the effect upon 
the moon’s mean motion of those which strike it only a minute 
fraction of the observed acceleration, still less can any action of 
those passing near the moon have any appreciable effect. 
Papers were also read by Prof. Harkness on the flexure of 
transit instruments ; by Prof. Hough, describing some improve- 
ments recently introduced in the printing chronograph, first 
designed and brought into use by himself at the Dudley Observa- 
tory in 1871, by Prof. Burkitt Webb, describing a method of 
using polar coordinates, by transferring the origin from the centre 
to the end of the unit radius, thus substituting (7-1) for 7, and 
then using the length of the arc and the distance out from its 
end upon the radius vector, as w and y are used in rectangular 
coordinates. He found this a very convenient transformation in 
the application of polar coordinates to the discussion of Amsler’s 
planimeter ; and, pointing out, that by substituting infinity for 
unit-radius in the equations thus transformed, they were reduced 
to those of rectangular coordinates, he thought this transforma- 
tion of polar coordinates might be found generally useful. 
In this section also Mr. Rockwell presented some results of 
his observations for time and latitude with the almucantar, an 
instrument devised by Mr. Chandler, of the Harvard College 
Observatory, a year or two ago, which promises at least to 
furnish an entirely new and radically different method of attack- 
ing the question of absolute positions of the stars, and very 
probably far to surpass all others in accuracy, on account of its 
freedom from systematic errors. The results thus far published by 
Mr. Chandler seem fully to confirm all that was expected of the in- 
strument ; and it is probably not too much to say, that it is the most 
important addition of the present century to the instruments and 
methods used in the determination ef absolute star positions. 
