ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 297 



MICEOSCOPY. 



A. Instruments. Accessories, etc.* 

 (1) Stands. 



Old French Microscope by Joblot. — This curious old Microscope 

 (fig. 29) has been acquired by the Society for its collection, and was 

 exhibited at the Meeting on March 18. It is one of three forms in- 

 vented about 1716 by L. Joblot, " Professeur Royal en Mathematiques 

 de l'Academie Royale de Peinture et Sculpture, demeuraut sur le quay 

 de FHorloge du Palais, au gros Raisin," and is described by him in his 

 work, Descriptions et usages de plusieurs nouveaux Microscopes, pub- 

 lished in Paris 1718. 



Joblot states in the text that the Microscopes designed by him were 

 made for him by M. le Febvre, Ingenieur en Instruments de Mathe- 

 matiques, but the present model bears the inscription : " J. Langlois, 

 Eleve du Sieur Butterfield, aux Amies d'Angleterre, a Paris," and, 

 moreover, is richly engraved with ornate designs on the handle and 

 principal surfaces, which are not shown in Joblot's plates. Langlois 

 and his master, Butterfield, are both known as noted makers of astro- 

 nomical quadrants, sundials, etc., in Paris, in the early part of the 

 eighteenth century, and it is probable that this Microscope was made by 

 the former some years after the publication of Joblot's description, say 

 about 1720. 



The design of this old Microscope is very peculiar ; it is used by 

 holding against the sky or a candle. The handle consists of a some- 

 what flattened brass cylinder, octagonal in cross section, supporting a 

 stage to which a brass-bound glass plate can be fixed. Below this is a 

 tubular diaphragm, called "le canon" by Joblot, lined inside with 

 black velvet, and with a stop at each end, an effective device for giving 

 the best possible definition. (In 1831 Hugh Powell made, and probably 

 re-invented, a similar cylinder diaphragm for the Microscope designed 

 by Cornelius Yarley.f) In front of the object-stage is the objective 

 carrier, fixed to a movable arm actuated by a large focusing-screw ; the 

 carrier receives the brass plates in which the objectives are mounted. 

 The objectives consist of bi-convex lenses of various focus, about \ in. 

 in diameter, held between two brass plates pierced with very small holes, 

 so that only the centre of the lens is used, thus reducing the aberration 

 and giving a fair definition, in the same manner and on the same plan as 

 is found in Leeuwenhoek's Microscopes ; the two brass plates are not, 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



t See this Journal, 1900, p. 232, fig. 74. 



June 17th, 1914 x 



