I 4 
Scientific Progress of the Past Year . [January, 
as the density of the gas. Although dimensional considera- 
tions have been shown by previous writers to have an 
important bearing on the Theory of Gases, still his experi- 
mental results form an important contribution to our know- 
ledge of the subject ; and in his theoretical investigation he 
has attacked with vigour, and not without success,, some 
elements of the problem avoided by his predecessors in this 
field of research. . , . 
Photography has of late years become so completely the 
handmaid of Physical Science, and has so constantly 
responded to the calls of its master, that its progress, how- 
ever rapid and however effeftive, has come to be taken 
almost as a matter of course. But the step which Captain 
Abney appears now to have taken lies entirely out of the 
ordinary line of advance. M. Becquerel, as is well known, 
succeeded some years ago in producing natural colours by 
the agency of light, one specimen of which— a solar 
spedtrum — was given to me some three years since by 
M. Cornu, and which, through being carefully preserved in 
a tin box, retains all its chromatic features. . Captain Abney 
' has now taken up the subject again, and believes it probable 
that the colours obtained by this process may be preserved 
unchanged when exposed to ordinary daylight.. His sug- 
gestion as to the physical causes of the colour is interesting, 
and leads us to hope that we may hear more upon the 
It W as at one time thought that Science and pradtical life 
were essentially distindt, and that in their cares and their 
purposes, in their sorrows and their joys, neither inter- 
meddled with the other. But in proportion as it has been 
gradually recognised that Science, and even Philosophy 
itself is based upon experience, so has their distinction 
gradually faded from our view. And, among many other 
instances of forecasts in this dire&ion by far-seeing men, I 
may adduce the dream of Babbage, that mathematical cal- 
culation might be reduced to mechanism, and that the data 
of many problems both of physics and of life might be 
handed over to an engine which would work out the results. 
That dream of his was as nearly realised as any dream of 
his ever could be realised ; for the merit and the charm of 
the man himself, and the fascination which he threw about 
all his projects, were derived from the fadt that, at whatever 
rate realisation followed, his ideas flew faster and faster still 
and outstripped them all. And if, in the machinery for 
complicated calculation designed by the Brothers Thomson, 
rnuch more has been actually achieved, than ever before, it 
