248 
&ir //. Davy and Dr. IV , IVoollaston. 
* - - M*. [Acd. 
A question which I put successively to each of these distinguished philosophers, 
. ! s »ow how very differently a subject may be viewed by minds of even the 
highest order. 
About the time Mr. Perkins was making his experiments on the compression of 
watd , 1 was much struck with the mechanical means he had brought t > bear on 
the subject, and was speculating on other applications of it, which I will presently 
mention. r 1 
Meeting Dr. Woollaston one morning in the shop of a bookseller, I proposed this 
question : It two volumes of hydrogen and one of oxygen are mixed together in a 
vessel, and if by mechanical pressure they can be so condensed as to become of 
the same specific gravity as water, will the gases, under these circumstances, unite 
(combine) and form water? “ What do you think they will do?” said Dr. W. I 
replied that I should rather expect they would unite. “ I see no reason to sup- 
pose it, said he. I then enquired whether he thought the experiment worth 
making. He answered that be did not, for that he should think it would 
certainly not succeed. 
<< ^ f ! W 5??* after ’ 1 2 * P r °P° sed the same question to Sir H. Davy. He at once said 
icy will become water of course and on my inquiring whether he thought the 
experiment worth making, he observed that it was a good experiment, but one 
which it was hardly necessary to make, as it must succeed. 
These were offhand answers, which it might perhaps be hardly fair to have 
nmorded, had they been of a person of less eminent talent; and it adds to the 
curiosity of the circumstance to mention, that I believe Dr. Woollaston’s reason for 
supposing no union would take place, arose from the nature of the electrical rela- 
tions of the two gases remaining unchanged ; an objection which did not weigh 
with the philosopher whose discoveries had given birth to it. 
[The result of the experiment appeared, and still appears tome, to be of the 
highest importance ; and I will shortly state the views with which it was connect- 
ed. llie next great discovery in chemistry to definite proportions will be 
to find means of forming all the simple unions of one atom with one, with two, 
or with more of any other substance; and it occurred to me that the gaseous bodies 
presen ec t ie fauest chance of success ; and that, if wishing, for instance, to unite 
tour atoms of substance with one of another, we could, by mechanical means, 
reduce the mixed gases to the same specific gravity as the substance would possess 
which resulted from their union ; then either that such union would actually take 
P a r tic . es the two substances would be most favourably situated for 
would ini! i Ca 0r, f * oJo ctncity, or other causes, to produce the combination. It 
cumstancM foll ° w > tl ! a \ combination should take place under such cir- 
sZld Z , G f° S - f r ? ab j e P r T rti0n in which f lie atoms unite, 
eSLent^arTS *“?“*?* a fluld of the ^ust specific gravity : but until the 
no^ be produced.] ^ ^ ^ Certain> that 0ther combinations might 
to rhpmi2^« f* ir . mt ? ness of tbe Fancies of bodies submitted by Dr. Woollaston 
forhine n yS i S -’ haS CX . Clted * he adniiration of all those who have had the good 
knowT r,ment8 ; and the metLods he e “p ,o > ed 
edt a ^%r. me , tl, f t a £ r T t mistake exists on ll,e subject. It has been adduc- 
es of the i nr i,v;,)f, e 1 l( S " ucd ' P rove the extraordinary acuteness of the bodily sens- 
to his nfd o^h dUal r a circuI V stance which, if it were true, would add but little 
iTght attrsee in f raCte V / "" however Alined to view it in a far different 
knowledge 1 ° De ° 1 ie natlmd results of the admirable precision of his 
I rememberTn!r^ ny •”^ POI tUn ’ t - eS V-* aVe en j°7 ed of seeing his minute experiments, 
acuteness of his 1 noti ced any remarkable difference in the 
of smell from rli ! ' r * acu ties ’ cither of his hearing, his sight, or of his sense 
never showed S ° ° ier persons who possessed them iu a good degree. He 
invisible to mv , an u most pjeroscopic wire, which was visible to his and 
sounds inaudible^ t, !* P? eveu 1,1 the beautiful experiments he made relative to 
mine although sens’ll Iain e . ans ’ be never produced a tone which was unheard by 
the case bv most of\ i V ° ', 1S < a ‘ ’• and 1 believe this will be found to have been 
enquiries and who ” !'° se . m j. nds had been much accustomed to experimental 
It ?al! their faculties unimpaired by illness or by age. 
de Pended Ti , *7 va ua , e property on which the success of such inquiries 
2 ‘ st 101,1 the perfect attention which lie could command, and 
^his was at Mr. South’s observatory and the object. 
