THE MICROSCOPE. 305 
whim ; it is the result of personal experience. I used a “Stove- 
pipe” and a French Triplet for several years before I learned 
there was anything better, and I am sure, of a fact I know, that 
their use did my eyes irreparable injury. 
On first class American stands a useful contrivance is applied 
to the lower end of the body, and named the safety nose piece. 
It consists of a short tube sliding easily within the body, and 
pressed upon by a spiral spring so that when forced upward, the 
pressure of the spring tends to return it to its former position. 
Its use is to protect high power objectives and the object also. 
High power lenses usually have a short working distance, so 
that there is danger, while focussing, of touching the front of the 
lens against the glass slip, a thing that every careful microscopist 
is anxious not to do, since the thin glass cover over the object 
may be cracked, and the lens may be scratched or broken, a 
much more serious matter than the breaking of a cover glass. 
But should such an accidental contact occur, before injury can 
be done, the safety nose-piece will slide upward, at once reliey- 
ing the pressure on the objective and calling the microscopist’s 
attention to the danger. But any microscopist who will focus 
an. objective while looking through it almost deserves to injure it. 
Another interesting and often useful device on first class 
American stands and a few foreign ones, is the scale and vernier 
on the side of the body and the arm, for the measurement of 
the working distance of objectives. It is never found on smaller 
and cheaper stands, where it might well be applied without 
great additional cost, and be used to assist the beginner in focus- 
sing his ojectives. However, it is not there, and at best it is 
only a luxury which need not be further discussed. 
THE DRAW-TUBE. 
On the majority of stands a draw tube will be found within 
the body if the latter is of standard length. On those whose 
body is shorter than ten inches, the draw tube is used only to 
make the extension to the standard, and no additional one will 
be on the instrument. The length of the draw-tube is usually 
almost that of the body, so that it will lengthen the latter 
enormously when fully extended, and correspondingly increase 
the magnifying power. Its upper end commonly projects some- 
what beyond that part cf the body, affording a means of manip- 
ulation, and for carrying the eye-piece. 
