1892.] MICROSCOPICAL JOURNAL. 167 



3 A is an illustration of the clip in use as seen from above, and 

 Fig. 2 B is an end view of the same as seen from a section 

 through the cover-glass. The clip should be made of rather stout 

 springy wire, so as to grasp the slide firmly. This clip will be 

 less liable to shift or become detachetl from the slide ; and it has 

 the advantage of being suitable for rectangular as well as circular 

 cover-glasses. — S. Pace, in Hardxvick's Science- Gossip. 



A Cheap Camera.— Cut a hole in one end of a cigar box and 

 insert a piece of metal in which is a very fine hole. Blacken the 

 whole inside of the box with dead black varnish, and close every 

 crack so that not a ray of light -shall enter except through the 

 small hole. At the other end a groove may be made into which 

 to insert the sensitive plate and the lid must be light-tight. A 

 lens is not necessary, but the hole must be such as is made by a 

 pin point, must l)e perfectly round and without irregular edges. 

 A watchmaker can drill such a hole very easily. Tell him to 

 make it i-5oth inch.- — Work. 



To Arrange a Photomicrographic Dark Room. — A sim- 

 ple dark closet, large enough to contain a table and a shelf or 

 two, may be u.sed. The necessary materials are a ruby lantern, 

 three flat trays, or even plates, if large enough to contain the 

 photo plates, a glass graduate, a small scales, and several bottles 

 for solutioiis. The water supply may be taken from a pail with 

 a rubber tube in the side, furnished with a spring clothes-pin or 

 clip ; the waste water may fall in a pail below ; a negative rack 

 and a 3-inch camel-hair brush are conveniences. The chemicals 

 will depend upon the formula recommended by the maker of the 

 dry plate used, but the following specimen list will do the work : 

 Soda sulphite, eikonogen or hydroquinone, potassium carbonate, 

 and potassium bromide, for developing ; mercury bichloride for 

 intensifying ; red prussiate of potash for reducing ; soda hypo- 

 sulphite for fixing. A printing outfit for paper prints would 

 include one or two printing frames. Sensitized paper, gold 

 chloride, soda acetate, card mounts, and two flat trays for toning 

 and fixing. Washing prints means prolonged soaking in any 

 convenient vessel. Vols. VI and VII of the A. M. Microscopi- 

 cal Journal contain a series of excellent papers on photomi- 

 crography, by R. Hitchcock. 



MICROSCOPICAL MANIPULATION. 



Collecting Terrace Dust. — Mr. W. J. Simmons, of Cal- 

 cutta, sends us a small packet of dust from the roof of a house in 

 Calcutta, and adds a note descriptive of its collection. 



'' Our houses in Calcutta are all flat-roofed. A parapet sur- 

 rounds the terrace, the latter being often an extensive sur- 

 face, which receives a great deal of dust of all sorts ; such 

 dust is drifted by the wind into the leeward corners of the 



