176 Answers to Quertes. 
instance, between Zeiss’ (105°) and + (110%) (10-inch tube) 
there is 13s. difference; Beck’s is 25s. difference ; Hartnack 8s. 
The reason a 4 is so common is that short-tube (foreign) instru- 
ments have generally a $-inch and }-inch with them correspond- 
ing to the English 1-inch and 4-inch objectives. 
J. G. P. VEREKER. 
396.—Microscope Lamp.—It seems to me there is no more use 
in purchasing an elaborately-finished and expensive lamp for 
microscope work, than to purchase a case, beautifully finished 
with plated corners and handle tor containing one’s microscope. 
I think most microscopists will admit that an ordinary paraffin 
lamp, such as can be purchased for rs., will answer every purpose, 
providing the flame of the lamp and the mirror of the microscope 
are parallel. My method is to place the lamp about three feet 
from the microscope, employing a plano-convex lens of about 24 
inches diameter, throwing parallel rays into the plane mirror, 
thereby giving ample illumination when using the inch objective. 
Thus, for illuminating for use with the quarter inch, I either draw 
the lamp and lens nearer, or turn the convex side of the mirror, 
so as to concentrate the parallel rays coming from the lens. I 
think J. H. will find this illumination ample for his 4 objective. 
He Aueye 
397.—Camera Lucida.—As J. H. has a “ Star” microscope, he 
cannot do better than procure a camera lucida as supplied by the 
maker of his instrument, and if economy is an object (as it gene- 
rally is to most scientists), he will have no cause to complain. My 
own instrument is a ‘‘ Star,” and I have found all the accessories I 
have purchased to be of first-rate workmanship. H. Ax je 
398.— Animal Intelligence.—Sir John Lubbock has, I believe, 
been carrying on a series of experiments with an intelligent dog. 
The animal has been taught “ to read ”—that is, to recognise certain 
written symbols by seeing them constantly associated with familiar 
objects. A lady some years ago taught an exceptionally bright pet 
dog to pick outa simple tune on the piano. But I venture to 
think that these and similar experiments, though carried out with 
admirable patience, have not been so successful as they might be, 
if carried out on evolutionary principles. An intelligent dog 
should be chosen, and carefully taught to the limit of its capacity, 
the utmost care being taken of the animal’s bodily health, and that 
it should enjoy itself as naturally as possible when not under tuition. 
The puppies of this dog should be equally carefully trained, and 
so on generation after generation. The early age at which a dog 
breeds would enable an observer to note the progress which would 
be made by several generations of dogs, and I cannot help think- 
ing the novel experiment would have a very interesting result. 
Animals have been bred to almost any shape, size, colour, and 
