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III. On Photometry in connexion mth Physical Optics, 
By R. Potter, Esq.^ B,A., F.C,P,S., Medical Fellow of 
QiieeiHs College^ Cambridge‘S, 
Photometry should have excited some attention 
amongst scientific men, could scarcely fail of proving a. 
cause of satisfaction to the writer of the present paper, who 
had several years ago urged its great importance in laying an 
experimental foundation in Physical Optics. If the su^ect 
had been approached in a philosophical spirit, with a real de- 
sire to find out the truth according to the principles laid down 
by Lord Bacon, that satisfaction must have been the writer’s 
privilege. Very different however has been the notice it has 
called forth. 
The dazzling fruits of Fresnel’s genius had so blinded the 
scientific world, that it has been held to be presumption to 
examine minutely the accuracy of his results, although his 
constitution of mind must have indicated the need of this, to 
the most cursory reader of his various papers. We there see 
the zeal of the advocate to carry his point, overruling his 
judgement, and leading him to make objections against the 
theory he opposed, which were frequently either incorrect in 
their foundation, or were of trivial importance. 
It matters little to say such and such things are in them- 
selves improbable or unintelligible; for if the theory give re- 
sults in accordance with natural phaenomena, we are bound to 
receive it, although many of its consequences should seem 
strange and even inadmissible at the first view : thus, I con- 
ceive, no one would be justified in rejecting the undulatory 
theory of light, or any other, if its results were in accordance 
with experiments. 
The fashion of pinning their faith on Fresnel’s sleeve having 
become general amongst the influential in learned societies, 
and amongst the most eminent in mathematical attainments, 
it was natural that minds of smaller calibre, or reputations of 
smaller weight, should feel it a readier and surer way to ho- 
nours and distinction to follow in the tide, without venturing 
to dispute the judgement of their superiors or to question their 
infallibility. Under such circumstances the mere analyst must 
find himself floating in the tide with those who claimed a more 
})rofound knowledge of experimental philosophy, and who 
were sure to applaud the aid he rendered to tlie common 
cause in symbols and formulae, of which they were frequently 
as little able as willing to investigate the accuracy. 
* Coimminicatecl by the Author. 
