1442 



Journal of Applied Microscopy 



ing on Velox I proceed as follows : Six frames are prepared and arranged on 

 the six sides of a hexagonal wire frame on which are stretched two thicknesses of 

 white tissue paper. 



This screen is about six inches in diameter, six inches deep, and open at 

 the top. The printing frames are placed at irreg- 

 ular distances from the screen, according to the 

 density of the plate in each case. 



A bit of magnesium ribbon about one and one- 

 half inches long is then ignited in an alcohol flame 

 and instantly placed within the screen near the 

 center. This prints all six pictures at once and 

 they are ready to be developed. The screen pre- 

 vents the edge of the opaque from printing up as a 

 sharp line. The use of the magnesium light greatly 

 increases the rapidity with which the prints may 

 be produced and also contributes not a little to the 

 sharpness of the image. 



Of course, with the simple appliances here 

 described, the highest de- 

 gree of critical photography 

 may hardly be attempted. 

 Nevertheless, it may be 

 readily seen, from the 

 samples herewith submit- 

 ted, that illustrations may 

 easily be secured, sufficient- 

 ly accurate for practical 

 purposes. No doubt a bet- 

 ter apparatus is a thing to 

 be desired. But, if the matter of expense must be taken into account at all, 

 the apparatus which we have here described and successfully used will com- 

 mend itself to many who might be prevented by the consideration of cost 

 from attempting experiment in this most fascinating field of work. The results 

 of our labors in this direction will form the subject of a descriptive paper pres- 

 ently to appear in the Bulletin of the Laboratories of Natural History of the 



Fig. 4. 



Fig. 



State University of Iowa. 

 University of Iowa. 



P. C. Myers. 



THE 5 mm. APOCHROMAT, AFTER PROF. CHARLES S. HASTINGS, IN THE 

 PHOTOGRAPHY OF DIATOMS. 



We are in receipt of a very interesting series of photo-micrographs of diatoms 

 from Honorable A. A. Adee, Washington, D. C, made while testing a 5 mm. 

 apochromatic objective after the formula recently computed by Prof. Charles S. 

 Hastings, Sheffield Scientific School, Yale University. 



The following brief notations, in connection with data which show subject, 



