ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 



647 



of the carbon holders, which have the terminals cast in one piece with 

 them ; and the adjustments for taking upiwear in all parts. 



Locke's High Power Jet.*— This jet (fig. 147) made by P. W. 

 Paul has a mixing chamber of new design placed next to the inlet valves 

 and connected to the jet by a long delivery tube, thus ensuring perfect 

 mixing of the gases and silence under high pressure. 



Fig. 147. 



Leppin and Masche's Projection Apparatus with Optical Bench 

 Extension.! — The main idea of this apparatus is to produce an initially 

 simple instrument which should be capable of additions as required, so 

 as to render it capable of performing all the most varied purposes 

 expected from such apparatus. Fig. 148 shows the arrangement for 

 simple projection. The iron camera is lined within with asbestos, and 

 has two doors : in addition to the ordinary mode of ventilation there is 

 also a removable outlet for the warm air. The condenser is of 130 mm. 

 diameter. The achromatic Petzval objective has 54 mm. diameter, 

 130 mm. focal length, and diaphragms. The simple form includes also 

 an object-holder, a stage, and a bench with three riders. Slides of 

 85 by 100 mm. up to 90 by 120 mm. can be projected, and a magnifica- 

 tion of 30-40 diameters attained. Fig. 149-shows the section of the 

 twin rails on which the riders slide. The two prismatic bars, at right 

 angles to each other, give smoothness of motion, security of position, 

 and facility for quick interchange of parts. This arrangement is an 

 essential novelty in the apparatus. Clamping screws are not required, 

 and the time necessary for tightening them consequently saved. The 

 apparatus is installed on a travelling table. It is thought that this 

 mobility will be useful and lead to further economy of time. The 

 height of the table is so designed that projection can be made over the 

 demonstrator's table, and the images received on a screen at a suitable 

 height. Moreover, it is pre-supposed that the apparatus would be 

 stationed near the lecturer's table for use as required, and thus place 



* Catalogue Optical Convention, 1905, p. 198, fig. 9. 



+ Central.-Zeit. f. Opt. u. Mech., xxvi. (April and May 1905) pp. 98-4, 105-6 

 (6 figs.}. 



