336 THE MIcroscope. 
In some of the earlier stands by Mr Tolles, that celebrated 
maker adopted a curious method of fine adjustment by a rotat- 
ing ring attached to the nose-piece. The movement was very 
smooth and pleasant, but although I have had no extended ex- 
perience with it, the constant use of the collar in that situation 
has always seemed to be rather awkward and inconvenient. The 
method was adopted by Mr Tolles alone, so far as I know, and 
only on some of his stands, which are now seldom in the market. 
In his largest and most complete instrument, he made use of 
the screw and lever to the nose-piece of the body. 
It is scarcely necessary to advise the beginner to select a stand 
with the fine adjustment at the back of the arm. He can hard- 
ly fail to do so if he buys a new American instrument, as most 
of these are supplied with this most praiseworthy arrangement. 
There are English stands in the American market with the old 
form on the nose-piece, and in other respects these are good 
instruments, but the beginner will find greater convenience and 
greater satisfaction in the use of the American models. 
The milled head of the fine adjustment screw on all first class 
stands, and on some of the less expensive, notably on Messrs J. 
W. Queen & Co.’s Acme No. 3, has the upper surface graduated 
for the measurement of the thin glass always covering micros- 
copic objects when permanently mounted. This glass varies a 
good deal in thickness, and since its presence influences the 
action of the objective, it is often important to know just what 
that thickness is. The value of each graduated space on the 
wheel depends upon several contingencies, seldom being the 
same in any two instruments by different makers. What that 
rule is the dealer wiil tell the purchaser if asked. On my own 
stand the distance between two lines is equal to an elevation or 
depression of the body tube for the one one-thousandth of an 
inch. 
_ProropLasM.—Protoplasm, simple or nucleated, is the formal 
basis of all life. It is the clay of the potter; which, bake it and 
paint it as he will, remains clay, separated by artifice, and not 
by Nature from the commonest brick or sun-dried clod.— Hualey. 
Wernich has shown that porous bodies which contain bacteria 
part with the germ even with a very moderate movement of air 
through them.—Report of the Maine State Board of Health. 
