166 THE AMERICAN MONTHLY [Sept 



and finally into 96 per cent spirit. Rub dry with a piece 

 of soft leather, and pass tliroug^h a flame. — /V/. Z/^., xlii., 

 762. 



Royal Microscopical Society. — At the last meeting- the 

 president referred to the loss the society had experienced 

 in the death of Dr. Henry Perigal, who died at the advan- 

 ced age of 98. He then exhibited and described two old 

 microscopes, one of which, made by Benjamin Martin, 

 probably dated from about 1770. It had two concave 

 mirrors, one of 4in. and the other of 9in. focus. The 

 optical part was curious, having- a fixed black lens in the 

 tube, which was common to all the objectives, each of 

 which was fitted with lieberkuhn. The other was an 

 antique instrument, with simple lenses fitting into one 

 another to increase the power. It seemed to be a copy of 

 one made by Mann and Ashcroft, somewhere about 1740, 

 and was made by Gary. He next called attention to an 

 excellent lithographic portrait of Prof. John Queckett, the 

 work of Wm. Lens Aldous, whose son had presented it to 

 the society. Mr, Fredk. Ives exhibited a camera lucida 

 which he had devised. It was one he had obtained from 

 Messrs. Swift, and he had slig-htly modified it by depos- 

 iting- on one of the inside faces of the compound prisma 

 very thin specular film of silver, throug-h which 

 it was possible to see the pencil without having to 

 centre the eye, as was the case where the film was opaque 

 with a small hole in it to look throug-h. 



After some remarks by Mr. Beck, Mr. Swift said there 

 was a difficulty in centering- the eye in the old form which 

 did not exist in the one before them, the pencil being 

 seen with ease while delineating the object under 

 observation. The president thought the device a val- 

 uable one, and preferable to that of a thick film of 

 silver with a hole in it. Mr. Ives also exhibited a mono- 

 cromatic g-reen screen, consisting- of dyed films between 

 two plates of g-lass, which he thought possessed advantages 

 over liquid screens. The one now shown would cut off 

 all beyond the F line on the blue side, including the ultra- 



