COUNT CASTRACANE, ON ILLUMINATION. 249 
penetrating the semi-horny substance of which it is composed. 
Several rows of hair pass through its upper attenuated edge, 
the roots of which are amply supphed with sebaceous glands ; 
the capillaries are very well seen in the specimen sent. It is 
the homologue of the inflected skin at the base of the human 
nail. 
I hope these few remarks may lead some one who has 
better opportunities of investigating the matter to take up 
the subject. 
On a New Metuop of Itiumination. 
By Count Franczsco CasTRACaneE. 
[Tue following letter from Count Francesco Castracane to 
R. P. Angelo Secchi originally appeared in the ‘ Atti della 
Academia pontificia de Nuovi Lincei,’ t. xvii, 1864, and has 
been forwarded to us by Sig. Castracane for publication, as 
he thinks the method of illumination therein recommended is 
one deserving of more notice than it appears hitherto to have 
received, and also because he entertains a hope that his desire 
to be assisted in the execution of the work he has proposed 
to himself may receive some support from English diatomists. 
Sig. Castracane has favoured us with a sight of some of his 
photographic figures of diatoms, with respect to which we can 
only say that we have never seen any to compare with them 
fer minuteness and clearness of definition ; and if he be equally 
successful in his projected work with other species, it cannot 
fail to be one of the greatest interest and importance to all 
who are concerned in the same branch of microscopic in- 
quiry. | 
A Letter from Signor ab. Conte Francesco Castracane degli 
Antelminelli to R. P. Secchi. 
In return for the kind interest you have taken in my faint 
endeavours to promote one among the numerous useful ap- 
plications of the photographic process in scientific research, I 
am desirous of explaining to you how far I have advanced in 
the subject ; and I do so with the more alacrity in the antici- 
pation that you may be willing to aid me very largely by your 
advice. 
Having been for a long time familiar with the various re- 
searches on the chemical action of light, which, since the 
marvellous discovery of Daguérre, constitute the whole of the 
