1899J MICROSCOPICAL JOURNAL. 159 



structed more than a dozen apparatus similar to that I 

 have endeavored to describe for the public laboratories 

 and for private teachers in the city in which I reside. 

 Magnesium ribbon is easily lighted if the end is dipped 

 either in paraffin oil or spirit of wine. To give another 

 illustration of the power of the light. I recently was 

 asked to produce some photo-micrographs of sand, one of 

 these being sand from the desert near Cairo, the other 

 singing sand from one of our western islands. I took 

 two 3X1 slides and spread a very little gum on them 

 then sprinkled the grains of sand on the gum. I placed 

 the slides on the stage of the microscope with a piece of 

 black paper behind, and using Zeiss 70 mm. apochroma- 

 tic, I obtained, by means of the gas in the room, as sharp 

 a focus as possible. I then, after the apparatus was in 

 order, placed a board alongside the camera to receive the 

 magnesium oxide as it dropped. I took a short piece of 

 brass tube and pushed about two inches of magnesium 

 ribbon through it, lighted it, and keeping it about a foot 

 from the slide, I burnt about eight or ten inches of the 

 ribbon by pushing the ribbon through the tube as it was 

 consumed. I used no condenser, and in this way I ob- 

 tained two very fine negatives. Lantern slides have been 

 made from these and they excite the admiration of every- 

 one who sees them on the screen. The light and shade 

 in the prominences and hollows in the sand grains are 

 beautifully rendered. They are at present being repro- 

 duced by a photo-mechanical process in the transactions 

 of a geological society. I have taken photo- micrographs 

 of such diatoms as Navicula lyra and N. splendida bv 

 means of Zeiss 4 mm. apochromatic without any conden- 

 ser by simply burning about six inches of ribbon. 



I cannot admire the persistent way in which photo-mi- 

 crographers will insist upon using oil lamps, even though 

 they are assisted by every possible optical accessory, when 

 they have at their command, if they choose to use it, a 



