1807] MICROSCOPICAL JOURNAL. 3 47 



in one cu. lutn. of the cell. A disc of glas.>? ruled us in 

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

 metal with a square cut out, as shown in fig. 10, may l)e 

 substituted. In either case the square must be of sucli 

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

 given combination of objective and oculai-, 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 

 witli, but for ordinary work the powers suggested are 

 sufficient. 



All this apparatus, together with bottles fjr collection 

 and note hook for records may be carried in a grip sack, 

 and this will be found generally the most convenient way. 

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

 ])artmeuts for holdinir the microscope, funnels, tube, 

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

 of njicroscopical sup[dies. — Science. 



AstroDomica! Photojirrnphv with Photoraicroj^raphic 

 Apparatus. 



A. CLU'fUliU MEKCEK, M. D. 

 .Syracusk, X. Y. 

 On the twentieth of October, 1892, ocmri'i'd a jiai'tial 

 eclipse ot'tlie sun, and my heliostat was })laced on a shelf 

 outside a .-outh window. Wiihin the room was a p.M- 

 trait lens of eight inches focus and a microscojie in the 

 small axial line. The substage condenser wms leniMv cd 

 and a camera connected with the <^ye end of the niicio- 

 sc()|)e tube. Such sunlight as fell on the uiinoi- of 

 the heliostat was reliected through the jioitiail bns 

 Tlic porti'ait b'us jtiojected .an i mage of the clouded sun's 

 disc, abiHit one-twelfth of an inch in dianuMer. in tln' 

 plane usually occupied by an object on the stage <>! the 

 inicrosco[)e. This tiny image was itself projerte 1 Iv 



