1897J MICROSCOPICAL JOURNAL. 347 



in one cu. mm. of tlie cell. A disc of glass rnled ms in 

 fig. 9 is the best form of micrometer, but a piece of thin 

 metal with a square cut out, as shown in fig. 10, may be 

 substituted. In either case the square must be of such 

 a size that it covers one sq. mm. on the stage with a 

 given combination of objective and ocular, and a certain 

 tube length to be found by comparison with a stage 

 micrometer. It is an advantage to have at hand higher 

 powers for a more thorough study of the organisms met 

 with, but for ordinary work the powers suggested are 

 suflScient. 



All this apparatus, together with bottles f.r collection 

 and note book for records may be carried in ,'i gri[) sack, 

 and this will be found generally the most convenient way. 

 It is possible, however, to make a neat box, with com- 

 partments for holding the raicroscoyje, funnels, tube, 

 vials, etc., and I respectfully submit this to manufacturers 

 of microscopical supplies. — Science. 



Astronomical Photography with Photomicrographic 

 Apparatus. 



A. CLIFFORD MERCER, M. D. 



Syracuse, N. Y. 



• 



On the twentieth of October, 1892, occurred a jKirtial 

 eclipse oftlie sun, and my hcliostat was placed on a shelf 

 outside a south window. Wiihin the room was a p>>r- 

 trait lens c»r eight inches focus and a micr()sco[)e in l!ie 

 small axial line. The substage condenser was rem')\ rd 

 ami a camera connected with the eye end of the micio- 

 scope tube. Sucdi sunlight as fell on the iniri'or of 

 the heliostat was reflected through the ]>oiiiait 1(mis 

 The portrait lens j>rojected an image of the ch^iKhMl sun's 

 disc, about one-twelft is of an inch in (liainc^lcr. in tin- 

 plane usually occupied by an object on th(^ stage <>l' the 

 inici'oscope. Tins tiny image w^s itself projected fx 



