The Microscope has, by the recent application of Achromatic Lenses, 

 become a standard instrument for investigation. That it is deservedly so, the 

 results obtained by it in the Sciences and Useful Arts, and the daily increasing 

 discoveries in the Animal and Vegetable Worlds, fully confirm. Hence it is 

 desirable to reduce the cost of its production, so that its usefulness may be 

 extended. This Mr. Pritchard has successfully effected in his new 

 f'ertical Tripod Achromatic Microscope, which is a steady efficient Instru- 

 ment, and capable of affording an endless source of instruction and amuse- 

 ment. In that Instrument Mr. P. has adopted the principles so fully laid down 

 in the ^^Microscopic Illustrations ;" no difficult)', therefore, can arise from 

 want of ample printed instructions for using it. 



Printed Descriptions may be had with each of the following Instruments, constructed 

 by Mr. Pritchard. 



£ s. d. 



Pocket Microscope, with rack aJjustment, in Case 1 18 



Vertical Tripod Achromatic Microscope, with one Set of Lenses, no Case. ... 7 18 



Jointed Tripod-stand Achromatic ditto, in Case 12 12 



Jointed Tripod-stand Achromatic ditto, with two Sets of Lenses, in Cabinet. . 18 18 



Jointed Tripod-stand Achromatic ditto, with Apparatus for Polarization ... . 26 50 

 Jointed Tripod-stand Achromatic ditto, best Mounting, full Sets of Lenses, 



and Apparatus 63 



New Garden Frame Thermometer , 15 



New Thermo-Hygrometer 18 



New Set of Slides, for Illustrating Geology by the Magic Lanthorn, with above 



100 Figures 3 16 



NAVAL, MILITARY, AND ASTRONOMICAL TELESCOPES. 



Drawing, Mathematical, and Philosophical Instruments of all kinds, 



MICROSCOPIC, POLARIZING, AND INFERENCE APPARATUS. 



Microscopic Objects. — Thin sections of Recent and Fossil Woods, Coal, Jet, 

 Charcoal, Oolites, Flint, Teeth, Bone, recent and fossil. — Insects and Dissections pre- 

 served in Balsam.— Zoophiles, Ferns, Algas, Fuci, Mosses, Shells, Scales, Ditto in Flint ; 

 FOSSIL INFUSORIA ; Crystals, Madrepores, Sponges, Tests, &c. 



Spectacle and Optical Instrument Manufactory, 

 162, Fleet Street, London. 



