138 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
August 17, 1872. 
guesses into the right direction ; and to that of the pas- ' 
sage of the Radius Vector over equal areas in equal times, : 
"by the notion of a whirling force emanating from the sun, < 
which we now regard as an entirely wrong conception 
of the cause of orbital revolution.* It should always be re¬ 
membered, moreover, that the Ptolemaic system'of astrono¬ 
my, with all its cumbrous ideal mechanism of “centric 
and excentric, cycle and epicycle, orb in orb,” did intel¬ 
lectually represent all that the astronomer, prior to the in¬ 
vention of the telescope, could see from his actual stand¬ 
point, the earth, with an accuracy which was proved by the 
fulfilment of his anticipations. And in that last and 
most memorable prediction which has given an imperish¬ 
able fame to our two illustrious contemporaries, the inade¬ 
quacy of the basis afforded by actual observation of the 
purturbations of Uranus, required that it should be sup¬ 
plemented by an assumption of the probable distance of 
the disturbing planet beyond, which has been shown by 
subsequent observation to have been only an approxi¬ 
mation to the truth. 
Even in this most exact of sciences, therefore, we can¬ 
not proceed a step without translating the actual pheno¬ 
mena of nature into intellectual representations of 
those phenomena; and it is because the Newtonian 
conception is not only the most simple, but it is also, 
up to the extent of our present knowledge, universal in 
its conformity to the facts of observation, that we accept 
it as the only scheme of the universe yet promulgated, 
which satisfies our intellectual requirements. 
"When, under the reign of the Ptolemaic system, any 
new inequality was discovered in the motion of a planet, 
a new wheel had to be added to the ideal mechanism,— 
as Ptolemy said, “ to save appearances.” If it should 
prove, a century hence, that the motion of Neptune him¬ 
self is disturbed by some other attraction than that exerted 
by the interior planets, we should confidently expect 
that not an ideal but a real cause for that disturbance 
will be found in the existence of another planet beyond. 
But I trust that I have now made it evident to you, 
that this confident expectation is not justified by any 
absolute necessity of Nature, but arises entirely out of 
our belief in her uniformity; and into the grounds of 
this and other primary beliefs, which serve as the founda¬ 
tion of all scientific reasoning, we shall presently in¬ 
quire. 
There is another class of cases, in which an equal cer¬ 
tainty is generally claimed for conclusions that seem to 
flow immediately from observed facts, though really 
evolved by intellectual processes; the apparent sim¬ 
plicity and directness 'of those processes either causing 
them to be entirely overlooked, or veiling the assump¬ 
tions on which they are based. Thus Mr. Lockyer 
speaks as confidently of the sun’s chromosphere of in¬ 
candescent Hydrogen, and of the local outbursts 
which cause it to send forth projections tens of 
thousands of miles high, as if he had been able to 
capture a flask of this gas, and had generated water by 
causing it to unite with oxygen. Yet this confidence is 
entirelv based on the asstimption, that a certain line 
which is seen in the spectrum of a hydrogen flame, means 
hydrogen also when seen in the spectrum of the sun’s 
chromosphere; and high as is the probability of that 
assumption, it cannot be regarded as a demonstrated cer¬ 
tainty,. since it is by no means inconceivable that the 
same line might be produced by some other substance at 
present unknown. And so when Dr. Huggins deduces 
from the different relative positions of certain lines in 
the spectra of different stars, that these stars are moving 
from or towards us in space, his admirable train of rea¬ 
soning is based on the assumption that these lines have 
the same meaning —that is, that they represent the same 
elements— in every luminary. That assumption, like the 
preceding, may be regarded as possessing a sufficiently 
* See Drinkwater’s ‘ Life of Kepler,’ in the Library of 
Useful Knowledge, pp. 2G-35. 
high probability to justify the reasoning based upon it; 
more especially since, by the other researches of that ex¬ 
cellent observer, the same chemical elements have been 
detected as vapours in those filmy cloudlets which seem 
to be stars in an early stage of consolidation. But when 
Frankland and Lockyer, seeing in the spectrum of the 
yellow Solar prominences a certain bright line not iden¬ 
tifiable with that of any known Terrestrial flame, attri¬ 
bute this to a hypothetical new substance which they 
propose to call Helium, it is obvious that their assump¬ 
tion rests on a far less secure foundation ; until it shall 
have received that verification, which, in the case of M r 
Crookes’s researches on Thallium, was afforded by the 
actual discovery of the new metal, whose presence had 
been indicated to him by a line in the spectrum not at¬ 
tributable to any substance then known. 
In a large number of other cases, moreover, our scien¬ 
tific interpretations are clearly matters of judgment ; and 
this is eminently a personal act , the value of its results 
depending in each case upon the qualifications of the 
individual for arriving at a correct decision. The surest 
of such judgments are those dictated by what we term 
“ Common Sense,” as to matters on which there seems 
no room for difference of opinion, because every sane 
person comes to the same conclusion, although he may 
be able to give no other reason for it than that it appears 
to him “ self-evident.” Thus while philosophers have 
raised a thick cloud of dust in the discussion of the basis, 
of our belief in the existence of a world external to our¬ 
selves,—of the Non Ego, as distinct from the Ego,—and 
while every logician claims to have found some flaw in 
the proof advanced by every other,—the common sense 
of mankind has arrived at a decision that is practically 
worth all the arguments of all the philosophers who have 
fought again and again over this battle ground. And I 
think it can be shown that the trustworthiness of this 
common sense decision arises from its dependence, not 
on any one set of experiences, but upon our unconscious 
co-ordination of the whole aggregate of our experiences ,— 
not on the conclusiveness of any one train of reasoning, 
but on the convergence of all our lines of thought towards 
this one centre. 
Now this “Common Sense,” disciplined and enlarged 
by appropriate culture, becomes one of our most valuable 
instruments of scientific inquiry; affording in many 
instances the best, and sometimes the only, basis for a 
rational conclusion. Let us take as a typical case, in 
which no special knowledge is required, what we are 
accustomed to call the “flint implements” of the Abbe¬ 
ville and Amiens gravel-beds. No logical proof can be 
adduced that the peculiar shapes of these flints were 
given to them by human hands ; but docs any unpre¬ 
judiced person now doubt it ? The evidence of design, 
to which, after an examination of one or two such speci¬ 
mens, we should only be justified in attaching a probable 
value, derives an irresistible cogency from accumulation. 
On the other hand, the improbability that these flints 
acquired their peculiar shape by accident , becomes to our 
minds greater and greater as more and more such speci¬ 
mens are found ; until at last this hypothesis, although! 
it cannot be directly disproved, is felt to be almost 
inconceivable, except by minds previously “ possessed ” 
by the “dominant idea” of the modern origin of man. 
And thus what was in the first instance a matter of dis¬ 
cussion, has now become one of those “self-evident” 
propositions, which claim the unhesitating assent of all 
whose opinion on the subject is entitled to the least 
weight. 
AVe proceed upwards, however, from such questions, 
as the common sense of mankind generally is competent 
to decide, to those in which special knowledge is re- 
: quired to give value to the judgment; and thus the in¬ 
terpretation ’of Nature by the use of that faculty 
comes to be more and more individual ; things being 
perfectly “ self-evident ” to men of special culture, which 
ordinary men, or men whose training has lain in a 
