the necessary data for altering the marking so that it may correspond to
1 cc _delivered_. Each 1 cc division is now divided into tenths by the
method described below. A final verification of the markings should be
made when the subdivision is completed.

_Subdivision of Graduations._--Mark out the spaces to be subdivided on a
sheet of paper. Take a reliable ruler on which any convenient length is
divided into the desired number and place it across the lines at such an
angle that the limits noted on the rule exactly bridge the gap. Now draw
parallel lines through the markings.

_Copying a Scale._--When a scale has been prepared on paper and it is
necessary to copy that scale on the waxed-glass surface for etching, a
convenient method is to employ a long wooden bar having a sharp needle
passing through it at either end. The scale and object to be marked are
fastened in line with one another, and the caliper bar is used from step
to step. The mark is made by moving the bar through a minute portion of
a circle, which provided that the bar is two or three feet in length,
will not introduce any perceptible error in a scale of say a quarter of
an inch in width. The arrangement is shown by Fig. 15.

[Illustration: Fig. 15]

_Graduating a Thermometer._--Assuming that the thermometer has been made
of carefully selected tubing in which the bore is parallel and free from
any small irregularities, we have only to fix the freezing point and
boiling point. The intervening space may then be divided into 100 (if
the thermometer is to be Centigrade) or 180 (if Fahrenheit). This
division may be carried out by the method given under "Subdivisions of
Graduations." A thermometer should not be calibrated until some weeks
after making, as the glass bulb tends to contract.

_Joining Glass and Metal._--It sometimes happens that one needs to make
a more permanent and less flexible joint between a glass and metal tube
than can be obtained by means of a rubber tube. To this end, any one of
three slightly different methods may be employed. In the method of
Chatelier one first coats the glass with platinum or silver, which may
be done by moistening the glass with platinum chloride or silver nitrate
and then heating to redness; a layer of copper is then deposited
electrolytically on the treated surface of the glass, and soldering is
carried out in the usual manner.

McKelvy and Taylor call attention to two other methods in the _Journal
of the