270 COEKESPONDENCE. 



Death of M. Alphonse de Brebisson. — It is witli much regret that 

 we have to announce the death of the distinguished naturalist, M. Louis- 

 AlphonsG de Brebisson, which took place on the 2Gth of April last. 

 M. de Brebisson was a most distinguished naturalist. Though his 

 absolutely microscopic work was small in amount, his additions to 

 natural history were both numerous and important. He had reached 

 his seventy -fourth year. 



Death of Mr. Hodgson, F.R.M.S.— We regret to have to record 

 the death, on the 4th of the month (May), of one of the oldest Fellows 

 of the R.M.S.— Eichard Hodgson, Esq., F.R.A.S., &c., of Chingford, 



Essex. 



COEKESPONDENCE. 



Sir David Brewster, Dr. Eoyston-Pigott, and the Photo- 

 graphic Camera Obscura. 



To the Editor of the ^Monthly Microscopical Journal.^ 



Sir, — When I read in your Journal for the month of February a 

 statement made by Dr. Eoyston-Pigott, that an " optical principle " had 

 been laid down by Sir David Brewster involving as it seemed to me 

 heretical doctrines, my curiosity was excited, and, as you are aware, I 

 troubled you with a few lines upon the subject. 



Now that I am, by the favour of Dr. Pigott's rei^ly, put in posses- 

 sion of the words of Sir David, I must confess to a considerable 

 amount of surprise, and I will add, of regret. As Dr. Pigott is 

 resi)onsible for the revival of what was generally regarded as a 

 defunct controversy, I will, with your permission, address these re- 

 marks more particularly to him. 



The doctrine to which I object is, that " Lenses of four inches 

 aperture and upwards, when used upon a minute object, yield nothing 

 but a mere jumble of hideous images, proceeding from upwards of 200 

 different points of the compass," &c. 



I object equally to the doctrine that, to get rid of the " distortion in 

 photographic images caused by the stereoscopic eifect of such a lens, 

 it is necessary, or proper, to reduce its aperture to that of the pupil of 

 the eye." 



With regard to the aberrations ascribed to lenses of four inches 

 aperture and upwards, it may be observed that whatever aberrations 

 may be created in any lens by rays of light diverging 150° as in the 

 microscope, it does not follow that where the rays are parallel, or 

 virtually parallel, as in the camera obscura (in which the divergency 

 never exceeds a single degree), the same aberrations will take place. 



In support of that view I may aj^jieal to the object-glasses at the 

 Greenwich Observatory, in which no aberrations of the kind exist ; 



