40 Dr. Maddox_, on Photomicrography. 
Stilly with these claims before us, what has been its pro- 
gress for the last ten years ? With us the climate may tend 
to hinder its advance ; those who would occasionally employ it 
may not be able to spare their time in the sunny hours ; hence 
we must look to artificial illumination. From experiments 
with the magnesium light, I am sure we have for very many 
objects an adequate source of illumination, though it remains 
to determine the best means for its ready application and the 
necessary correction for the actinic rays ; these are mechanical 
points. 
The value of the oxycalcium light has been already decided 
by the conjoint labours of Drs. Abercrombie and Wilson, of 
Cheltenham. By its use, and a very simple substitute for the 
bellows- camera, as described in the last July number of the 
' British and Foreign Quarterly Review and Medico-Chirur- 
gical Journal,'' they have produced some most charming 
results, remarkable for the softness of the shadows, delicacy 
of outline, and transparency in the detail. Doubtless we shall 
eventually be able to obtain, if advantageous, instantaneous 
pictures of the circulation in some of the most transparent 
forms of insects, or in aquatic larvse, especially when the 
blood-globules are of considerable size, and in transit appear, 
as it were, from their sarcode condition, often dragged into 
very oblong forms, which may help to determine the direction 
of the current, and when the insect will bear considerable 
compression without injury, so as to bring the irregular sur- 
faces into closer contact with the thin cover of the slide or 
top of the aquatic box. 
There are some of the confervoid Algae — as Drapernaldia 
Chcetophora — which have hitherto baffled many attempts. We 
cannot readily render the chlorophyll of the cells and at the 
same time preserve the fine terminating filaments ; these are 
mostly lost in the development. If we attempt to give colour 
to them by staining, the appearance of the chlorophyll in the 
Ipwer cells is quickly altered. 
It would be incorrect to judge of its general applicability 
by its failures in one or two classes of objects ; even if many 
of the Diatomacese have also to be excluded for more extended 
trials, may we not expect to obtain fresh advantages ? Al- 
though it cannot disclose the latent doings of the synthetical 
chemistry of organic existence, or display the rules of phy- 
sical destruction, it may largely assist in the elucidation of 
those questions which now rest on belief, and are open to the 
testimony of the controversialists of science. Indeed, we 
may expect, as the labours of individuals are collected and 
compared, additional superstructure will be furnished to the 
