Journal 



OF THE 



NEW-YORK MICROSCOPICAL SOCIETY. 



Vol. hi. JANUARY, 188V. No. 1. 



THE BROWNIAN MOVEMENT. 



BY H. L. BREVOORT. 



{Read January 2lst, 1887.) 



I have from time to time for the past four years given a 

 good deal of attention to this still unexplained movement. 

 As you all know, small particles of any substance, when sus- 

 pended in water, will show and continue to show for an 

 indefinite period of time, a rapid movement. Apparently as long 

 as the slide lasts, the movement will continue. I have slides 

 some four years old and the movement is as rapid now as on the 

 day they were mounted. Prof. Stanly Jevons says, if I remember 

 correctly, that, he had slides over ten years old which showed 

 the movement as when new. I have found the common water- 

 color paint, " flake-white " to give the most satisfactory results. 

 Rub a little of this up with water till the water is milky ; then 

 let it settle for a few minutes and decant the upper and clearer 

 portion of the liquid. Repeat this several times. Then mount 

 in a cell, say t^tt of an inch deep. Observe with a yi, or still 

 higher objective and the movement will be clearly seen. It is 

 best to make the cell of less depth, if very high objectives are to 

 be used. Finely powdered glass may be used in place of "flake- 

 white." Vermilion is a good material, but the particles are so 

 small and move so rapidly that it is difficult to observe them. 

 Carmine does not make a lasting slide, though a very effective 

 one while it does last. Cobalt makes a good slide, but the par- 

 ticles are very small. In all cases proceed to mount as directed. 

 The difficulty is that every one uses too much material in the 

 water. Use so little that no color is apparent to the eye in the 

 mounted slide, or, only a tinge at most. 



