168 Intelligence and Miscellaneous Articles. 
«Tt was my intention to have added a particular description of the 
individual which has been the subject of this memoir; but on care- 
fully inspecting the animal I find Dr. Traill’s elaborate description so 
accurate—(there really is no difference but sex at present)—that I 
should be needlessly occupying space if I inserted my own; and I 
beg, therefore, to refer the reader to that gentleman’s highly valuable 
papers in the ‘ Wernerian Transactions’. 
«« Since writing the above the cage in which our animal was con- 
fined has been enlarged and several barked branches have been nailed 
to a stem so as to form an artificial tree. ‘These branches he ascends 
with great activity, and frequently swings with his head downwards, 
holding on by his lower extremities, and recovering himself with 
greater agility than any rope-dancer.”—W. J. B. 
XX XI.—Zntelligence and Miscellaneous Articles. 
OPTICAL EXPERIMENT. 
GPE following description of an optical experiment will no doubt in- 
terest many of the readers of the London and Edinburgh Philo- 
sophical Magazine: this experiment is easily performed, and may be 
seen by several persons at the same time. 
Mr. Lipkens, of Voorburg, it is believed, was the first to notice the 
phenomenon, and on a recent visit to this country was so kind as to 
call the attention of the writer to the fact, and to allow of its being 
published in England. 
The apparatus which may be most advantageously employed for 
the development of this phenomenon, consists of astout hollow sphe- 
rical glass vessel about six or eight inches in diameter, with an open 
neck, to which should be attached, by cement or otherwise, a brass 
cap, furnished with a stop-cock. 
The experiment is performed thus: Pour into the globe a small por- 
tion of water, and then, by means of the lungs or of a condensing 
syringe, force air into it, the quantity being adjusted according to 
the strength of the globe. Ifa lighted candle or lamp be so placed 
that the flame may be viewed through the horizontal diameter of the 
spherical vessel while it is charged with condensed air, and supported 
at the same time in such a position that the neck with the brass cap 
and stop-cock are uppermost, then every time the finger of the operator 
placed upon the opening of the stop-cock so as to close it, is raised, 
a sudden and rapid escape of a portion of the confined air or vapour 
taking place, it will be observed that the image of the flame will ap- 
pear with a halo of coloured light. Generally the first escape gives 
a light yellow halo surrounded with a red circular fringe; the se- 
cond liberation a blue halo; the third shows a green halo, and in 
most cases the haloes are encompassed by a series of coloured rings. 
Before all the condensed air is allowed to escape, the water in the 
globe may be shaken about in it without any detriment to the ex- 
periment. 
The phenomena exhibited by this experiment (if dexterously per- 
