ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
591 
Brownian Movement.* — M. C. Maltezos adds a note to his memoir 
on the Brownian movement which appeared in the 4 Annales de Cliimie 
et de Physique ’ for Ajrril 1894. In that memoir he states that if 
the superficial tension is the same round a corpuscle in suspension, its 
effect will be nil. But this state of equilibrium ceases and the Brownian 
movement commences in the following cases : — (1) When the body has 
not the same superficial density throughout its surface ; and (2) when 
the liquid near the body is not pure. 
The author refers to a paper by J. A. Bliss j which has caused him 
to slightly modify his vieqrs. In that paper is described a series of 
observations made in order to discover the causes of the phenomenon 
of flocculation, i. e. the aggregation into flocks of finely suspended matter 
in water on the addition of a few drops of acid or solutions of different 
salts. The phenomenon of flocculation explains the observation made by 
Stanley Jevons that the Brownian movement is almost stopped by the 
addition of saline or acid solutions. The author, however, in his obser- 
vations found that after the addition of the saline solution particles form 
flocks when they are near to each other, and cease to show the Brownian 
movement when many unite together ; but there are others which simply 
enlarge themselves and continue to move. This latter phenomenon was 
explained by the existence, as revealed by a higher power, of finer 
particles near the larger ones. 
As the result of his observations the author concludes that the 
Brownian movement is a phenomenon of capillarity. For a particle 
sus])ended in a liquid he considers the two cases : (1) When the particle 
is near the bottom of the vessel or near another particle ; (2) when it is 
suspended in the middle of the liquid. 
(1) When the particle is near the bottom it is in a liquid which is 
not homogeneous, for quite near the wall and the bodies supported by it 
is a capillary liquid atmosphere. As the attraction solid-liquid and 
wall-liquid is greater (in pure water) than the attraction liquid-liquid 
and wall-solid, the potential energy is a minimum ; if the distance of 
the particle from the bottom is smaller than the sum of the two radii of 
molecular action (wall-liquid and particle-liquid), repulsions will result 
and the Brownian movement will be produced. 
The same thing should take place when the particle is near another 
in the middle of the liquid. 
(2) When the particle is far from the walls and other particles, if 
the liquid were quite homogeneous around it, the particle would not 
present the Brownian movement ; but if the liquid were not homogeneous 
either by reason of its salinity, or of the presence of the immersed 
objective, or of the superficial non-homogeneity of the solid, the differ- 
ence of the superficial tension which would result would suffice to push 
the solid in one direction or another, i. e. to communicate to it the 
Brownian movement. 
Micrographic Analysis.! — Prof. W. C. Roberts-Austen gives an 
account of a new branch of investigation, 44 micro-metallography,” or 
the application of the Microscope to the study of the composition of 
samples of metals, such as iron and steel. Dr. Sorby, in 1864, was one 
of the first to attempt to develop a method of investigating samples of 
* Comptes Rendus, cxxi. (1895) pp. 303-5. 
t Physical Rev., ii. (1895) No. 11. % Nature, xlii. (1895) pp. 367-9. 
