1H99J MICR0S(X)P1CAL .lOIIRNAL. 15'.* 



structed more thati n dozen api)aratu.s si[nilar to that I 

 liav(» endeavored to describe for tlie public laboratories 

 Mild for private reaciiers iti tbe city in whioli 1 reside. 

 \Iag-nesium ribbon is easily lighted if the end is dipped 

 cither in paraliin oil or spirit of wine. To give another 

 illustration of the power of the light. 1 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 weste-rn islands. I took 

 Uvo 3 X- 1 slides and spread a very little gum on them, 

 t lien sprinkled the grains of sand on the gum. 1 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 tul)e 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 [»ushing the ribbon through the tube as it was 

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

 tained two very line 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 

 lieautifuUy rendered. They are at present being repro- 

 duced by a photo-mechanical process in the transactions 

 of a geological society. T have taken photo- micrographs 

 of such diatoms as Navicula lyra and N. splendida by 

 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 plioto-rai- 

 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 



