ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 



129 



The " Student's Micro-Camera " is shown in fig. 22, and is intended 

 for plates 2^ in. x If in. It is made of mahogany, and is fitted to the 

 Microscope by cutting a hole in front and lining it with velvet, the eye- 



FiG. 22. 



Fot. 23. 



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piece being removed. After focusing, the camera must be removed from 

 the Microscope to the dark room, where the ground glass is replaced by 

 the plate. 



The " Superior Micro-Camera " (fig. 23) has a double dark slide which 

 avoids the necessity of removing the camera from the Microscope during 

 the operation, and the inside shutter (shown by dotted lines in the fig.) 

 enables the exposure to be made more easily without any danger of 

 shaking the apparatus. 



Photomicrography with Magnesium Light.* — Dr. E. Eoux recom- 

 mends a magnesium oxyhydrogen light for photomicrography. 



Common powered magnesia is mixed up with water to a stiff paste, 

 then stuffed into glass tubes of 4-5 mm. internal diameter. From this 

 it is squeezed out and then cut up into pieces 5 mm, long. These 

 pieces are rolled into balls and stuck on the end of a piece of platinum 

 wire. They are then exposed for three or four hours to a temperature 

 of 100°. They are then first exposed to the hydrogen flame of an oxy- 

 hydrogen burner, and afterwards to that of the oxygen. After this 

 treatment they are hard and unalterable in the air. 



One of these small pieces of magnesia will last for fifteen hours 

 straight off. The light is uncommonly effectual for photography, and 

 offers the advantage that it illuminates regularly, is not diffusive, and 

 remains fixed to the same point. 



Marktanner's Instantaneous Photomicrographic Apparatus. — 

 Dr. G. Marktanner points out that when single individuals out of a 

 great number of moving objects (e. g. fresh blood-corpuscles) are to be 

 photographed, the observer must be in a position, with apparatus ready 

 for the exposure, to wait for the instant when the moving object appears 

 in the field of view. Two conditions are to be noted : that the object 

 during the observation must be only moderately illuminated ; and, 

 further, that the observation must be made through a second tube 

 while the body-tube is connected in the usual way with the camera. 

 Tlie latter condition is fulfilled in the Nachet apparatus: it was the 

 consideration of the former which led the author to construct the new 



* Photogr. Wochenbl. Berlin, 1888, No. 5. Cf. Zeitschr. f. Wiss. Mikr, v 0888) 

 pp. 497-8. 



1889. K 



