"oSrnLlSris'S!'] NOTES AND MEMORANDA. 205 



the planes exhibit iiximcrous irregular cavities and linear chinks filled 

 np with crypto-crystalliue calcite ; in the latter substance, thus sitU' 

 ated, there are numerous beautiful examples both of ' stolons ' and 

 ' canal system,' — all clearly originating from crystals of malacolite." 



NOTES AND MEMORANDA. 



American Microscopes.— The recent Eeport of the Judges (Mr, 

 Wightman, Dr. Curtis, and Mr. Stevens) on the Pliilosoj)hical Appa- 

 ratus exhibited at the Exhibition of the Massachusetts Mechanic Asso- 

 ciation, held at Boston, in September, is highly favourable to Messrs. 

 Tolles. Of the specimens exhibited by the makers the Eeport says : — 



" The microscopes exhibited comprise a variety of instruments and 

 accessories, embracing much that is original and ingenious, and charac- 

 terized by nice workmanship) and elegance in appearance. 



" One large microscope with A and B Huyghens' eye-pieces, and 

 Tolles' patent solid C eye-piece, with micrometer, has a very ingeni- 

 ously constructed rotary stage, devised by Mr. Tolles, which is only 

 one-sixteenth of an inch thick. Its rotary movement is concentric 

 with the axis of the objective. It has also lateral movements by friction 

 rollers, and a sub-stage, movable by rack and pinion, for accessory 

 apparatus. 



" There are several other instruments intended for students, which 

 are much less elaborate. These are supplied with a one-inch and a 

 one-fourth inch objectives, both of second quality, and have coarse and 

 fine adjustments, and also the means for applying accessories. We 

 should also here mention a pocket achromatic triplet. 



" In the list exhibited, we find a binocular eye-piece, and a solid 

 eye-piece, both invented by Mr. Tolles ; and although the latter was 

 patented in this country by him several years ago, we were shown a 

 similar device, in fact nearly identical in every essential particular, by 

 a scientific friend, who has just returned from a sojourn in Europe, 

 where he purchased it as a new and valuable oculaire, one of the latest 

 improvements just invented by a microscope maker of celebrity in Paris. 



" Among the instrinnents on exhibition^ we find first-class objectives, 

 as follows : a one-inch, having an angle of aperture of 27° ; a half-inch, 

 with 60° angle of aperture ; a one-fourth, with 70"" angle of aperture, 

 and constructed with a Tolles' illuminator for opaque objects ; a one- 

 sixth immersion, with 150" angle of aperture ; and a one-tenth immer- 

 , sion, having an angular aperture of 175°. 



" It is mainly to improved object-iueces or objectives, as they are 

 more frequently termed, that the world is indebted for the means of 

 extending the limits of our knowledge through the revelations of this 

 valuable instrument. Since the middle of the present century, im- 

 provements have been made, and a degree of perfection approximated 

 in the construction of microscopic objectives, which twenty years ago 

 were pronounced by the best authorities as utterly unattainable. 



