Answers to Queries. IQL 
as the case may be, being much more easily printed than the old- 
fashioned |2- G. H. BRYAN. 
396.—Microscope Lamp.—The source of light in microscopic 
investigation is very important. The worst of all ordinary forms 
of artificial illumination is coal-gas ; and the best, at least in my 
experience, is petroleum containing camphor in solution and colza 
oil occupying an intermediate place between the two. In using a 
lamp, 2o direct rays should find their way into the eye of the 
observer except through the tube of the microscope. Next, 
exclude the red rays of the light from the eye. I do not think 
that any very great advantage is obtained by getting an expensive 
lamp. I have used a small household lamp, with a blue glass and 
a white (thick) paper shade over it, taking care to put a lump of 
camphor in the oil as above. ‘The lamp I now use, and which in 
my opinion is everything to be desired, is “ Parkes,” with cooling 
evaporator. It has a hood, at the back of which is a parabolic 
reflector, transmitting nearly parallel rays and removable for 
cleaning purposes, etc. At the front is a “‘light-modifier.” In 
this way work may be done and no heat worth mentioning is felt 
by the student, which is greatly to be desired. It may be bought 
of Ferris and Co., Bristol, for about a sovereign at the most. I 
am not sure if it is not even less. It is made to be useful for all 
purposes, and is constructed of brass. Swift’s lamp is good, but 
would be much improved by a glazed porcelain chimney with two 
opposite perforations, so as to avoid all extraneous rays passing to 
the eye. Browning’s lamp is very good, as are Collins’ Bockett 
and Fiddian’s lamp, made by Ross and Co. A beautiful lamp is 
that made by Wood and Co., Liverpool, for Messrs. Dallinger and 
Drysdale. A good, cheap, little lamp is Barclay’s ‘ Mikros,” of 
138 Regent Street, London (12/6), which is furnished with a 
silvered reflector and a powerful lens. It burns for seven hours 
without replenishing, at a cost of one-eighth of a penny per hour, 
and gives off very little heat. The German student’s lamp is 
good and cheap, and has an Argand burner. For books on the 
subject, see Carpenter, Hogg, April number Monthly Microscopical 
Journal, 1876, Vol. XV., Journ. Royal Microscopical Society, 
Journal Quekett Club, Vol. I., second series ; ‘‘On Microscopical 
Vision,” Nelson and Suffolk; and Gage ‘On Microscopical 
Methods” (50c.). ViccAL 
397.—Camera Lucida.—The vertical camera lucida (Beck’s, 
18/-) is a good one, and is used in an upright position, and is in 
other respects similar to Wollaston’s (horizontal, 1o/-). A small 
one may be made by using a cover-glass (white or blue), held at 
an angle of 45 deg., with the eye-glass in such a position that the 
centre of the cover coincides with the optical axis of the micro- 
