NOTES AND QUERIES. 129 

matter ;” we, therefore, beg to inform our readers that every care 
is taken to avoid mistakes, and if angle is only ‘a secondary mat- 
ter,” we ask, why is it that so much stress is laid upon it by the 
vendors? We argue that if an objective is bought as one of 95°, 
it should be more than 78°. It may be urged that the makers 
cannot produce the same aperture twice in succession, but that 
they can be much nearer than 17° is proved by the statistics of this 
department. Ifa purchaser does not receive what he asks for, the 
law provides that he can return it within a reasonable time. 
THE ELectric Licut ror Microscopy.—In Feb., 1881, we wrote 
to Mr. Swan of Newcastle, asking him to make us a special lamp 
for use in microscopic illumination, so that the direct light might 
be used with high powers, and also as an aid in photo-micrography. 
After some delay, a lamp came to hand, and we made many ex- 
periments with it, but on the whole were not completely satisfied 
with the results so far as cost was concerned. We found it much 
more economical for photo-micrography to use as a magnesium 
lamp. : 
It appears that Dr. Van Heurck, the diatomist, has been using 
Swan’s lamps, and a paper from his pen appears in No. V. of the 
Proceedings of the “Société Belge de Microscopie,” which we hope 
to translate in full for our next number. 
MounTING VoLvox GLOBATOR IN GLYCERINE JELLY.—Amongst 
fresh water Algze perhaps there is no more interesting object than 
Volvox. Its perfectly globular form, the outer delicate membrane 
or network which encloses the brilliantly green progeny, and, when 
freshly taken from its native water, its active rolling motion, render 
it particularly attractive. 
Various attempts have been made to secure this object as a 
permanent slide; camphor water and other Media have been 
employed, but, while the form has been retained, the natural 
colour of the Volvox has been lost, and with this much of its 
attractiveness. 
In order to retain colour in Algz, and indeed, all vegetable 
objects, Glycerine Jelly is advisedly the favourite medium, and in 
this the writer attempted the mounting of Volvox, boiling, &c., in 
the usual way. 
In one case he used a sunken glass cell and in the other an 
ordinary glass slip; in one case without pressure, in the other 
applying a clip to fix the cover glass. 
_ In each case, after a month’s time, the Volvox globator is perfect 
in form and colour, and the success of the attempt goes to prove 
that this Alga can be treated like any other, and may be boiled 
and pressed without the destruction of its shape. 
Jas. FLEMING. 
