628 SUMMARY OF CURRENT RESEARCHES RELATING TO 



horizontal steel rod. The hinder pair supports the double lamp-carrier 

 rotatory alwut a vertical axis. A Thomson lamp may be used as the 

 light source ; but a better result is obtained from a 30-ampere lamp 

 with right-angled carbons. This lamp is adjustable in the optic axis by 

 a lever. The usual vertical, horizontal and lateral centrings of the 

 light-source are now reduced to a perpendicular and lateral adjustment 

 of the lamp itself, a great gain in the case of an inexperienced demon- 

 strator. The lamp, moreover, whilst being moved up and down on its 

 carrier-pillars, is counter-balanced by a weight. This vertical movement 

 is, however, only required in the case of change to diascopic projection 

 of large section with right-angled reflected light. Both of these centric 

 positions are firmly secured by clamps. The rotation of the lamp 

 through 45° to the normal optic axis serves for the projection of objects 

 situated in a laterally incident light. On the front pair of legs stands a 

 "bearer of T-section diminishing upwards and carrying in its grooved 

 lower part the guide-nut for the perpendicularly movable large object 

 stage for the macroscopic objects. The bearer also carries the adjust- 

 ment arrangement of this stage operated by a cranked wheel. At its 

 top end the bearer develops into a circular frame for the reception of the 

 diaphragm arrangement. A strong horizontal steel rod finally connects 

 it with the lamp-carrier, and serves as a holder of the large projection 

 objective ; it also carries a diaphragm adjustable in the optic axis, and 

 on this diaphragm the screen-cloth is screwed. [The screen-cloth is not 

 shown in the figure.] The large condensers are mounted on the 

 horizontal lamp bearer, and both lenses are free for convenience of 

 cleaning. Lamp and condenser are arranged for tilting. The appliances 

 necessary for micro- and diapositive projection are so mounted on an 

 optical bench, which is fastened each way on two long T-carriers, 

 gripping the connected rod of the legs, that they can be moved either 

 way. They are held in centric and lateral position by strong clamps. 

 In order to diminish the possibility of a wrong position of any of the 

 parts, and to facilitate exchange of diapositives, the optical bench is 

 bowed underneath like a handle. The cooling trough and the dia- 

 positive holder are placed on the short arm. The author illustrates the 

 details of the various methods of projection by suitable figures, one of 

 which also shows the convenience of the bow in the bench as affording 

 hand-room in exchanging diapositives, as above mentioned. 



New Model of a Simple Movable Object Slide.* — G. Schorr has 

 found the following contrivance very useful in dealing with serial sec- 

 tions. A slab of glass, about 8 mm. thick and 9 x 13 cm. surface, has 

 a semicircular excision in one of the long edges, and on each side of this 

 and on the upper surface a naiTow strip of glass is cemented. The under 

 surface of the slab is divided into three strips. A, E, B (fig. 105), of equal 

 breadth, A and B being ground and E clear. In application A and B 

 are moistened with w'ater, or, better, with a mixture of glycerin and 

 water. The slab will then, by capillary attraction, adhere firmly enough 

 to the Microscope stage to retain any position which it may be required 

 to take ; at the same time a slight push-action is sufficient to move it. 



* Zeitschr. wiss. Mikrosk., xxiii. (1906) pp. 425-7 (1 fig.). 



