170 
Movement of Microscopic Particles 
[April, 
microscope, as in that of Dr. Carpenter (4th edition, p. 169), 
or in Griffith’s “ Micrographic Dictionary,” article “ Mole- 
cular Motion ” (3rd edition, vol. i., p. 498). 
The French naturalist and microscopist, Dujardin, appears 
to have paid special attention to this Brownian movement, 
which he describes with more minuteness and accuracy than 
any previous observer.* 
Griffith, the editor of: the “ Micrographic Dictionary,” 
seems to be almost the only other observer who has specially 
investigated this curious subject. His results are mostly 
correCt as far as they go.f He finds that all kinds of pon- 
derable matter, whether organic or inorganic, exhibit these 
movements when reduced to a fine state of division, and 
suspended in a liquid not too viscid or tenacious. He satis- 
fied himself that a single particle moves independently of 
surrounding particles. He rejects the explanations pre- 
viously suggested, such as the influence of evaporation, and, 
after unsuccessfully trying some experiments with electricity, 
leaves off with the candid conclusion that he knows no 
cause for the phenomenon. 
For a number of years past % I have occasionally occupied 
leisure time with experiments on this subject. For the mi- 
croscopic observations a good compound instrument is 
desirable, if not indispensable. I have used an excellent 
instrument by Dancer, of Manchester, the quarter-inch ob- 
jective of which, with the lowest eye-piece, usually suffices ; 
but, to observe the movements in all their perfection, I have 
found a good one-eighth inch objective, with a C or D eye- 
piece, to be useful. 
One difficulty is to find a convenient name for the pheno- 
menon. Brown called it molecular movement , and it is often 
so called in microscopic books ; but this is a very bad name, 
as the particles moving are of course not molecules. Some 
writers have called it the Brownian movement ; but this two- 
worded expression is very inconvenient, is not in any way 
descriptive, and gives perhaps undeserved honour to Brown, 
who was not its first discoverer, and did little more than 
make it generally known. Dujardin described the motion 
as one of titubation , from the Latin titubatio, which means 
staggering or wavering ; but this word is not elegant, and 
* Nouveau Manuel complet de l’Observateur au Microscope. Manuels 
Roret, Paris, 1843, pp. 58 to 60. 
f London Medical Gazette, 1843, vol. ii., pp. 502 to 506. 
t A brief preliminary account of my experiments was given in the Proceed- 
ings of the Manchester Literary and Philosophical Society for January 23th, 
1870 (vol. ix., p. 78). 
