r the telescopes at the proper angles. A position
circle of 75 mm. diameter, reading to degrees, is fitted to the instrument.
The slit has micrometer head.

Price, without grating, but including 60 degree prism #$75.00#

#Note.#--This spectroscope can also be used on a support for laboratory
work.

#Support# for above spectroscope. Price #$4.50#

#A602. Spectroscope# for telescopes from 6 in. to 18 in. aperture and
detailed description on application.

[Illustration: A 701]

#A701. Chronograph# for physical and astronomical work. This chronograph is
designed to meet the demand for a medium sized, well-made and accurate
instrument of this kind and has given very good satisfaction. The cylinder
is 15 cm. in diameter 25 cm. long, driven by strong, carefully made clock
work, fitted with friction governor. Two different speeds for the cylinder
can be obtained by means of change gears. The slow speed of the drum is one
revolution per minute, and at this speed the drum will run for a full hour.
The fast speed is 30 seconds per revolution. The carriage is driven by
means of a screw, the nut of which is made to disengage easily.

Price of the instrument complete with two pens and glass cover #$225.00#

#A701a. Chronograph#, the same as A701 but with only one pen. The carriage
is so constructed that a second pen can easily be added later. Price with
glass cover #$195.00#

#Note.#--Every instrument is carefully tested before being sent out and we
can guarantee the speed not to vary over 1-20 second during the full run of
one hour. Large temperature changes will not affect the speed of the clock.
A large number of the chronographs are in use and have given excellent
satisfaction.

[Illustration: A 702]

#A702. Prof. G. W. Hough's Printing Chronograph.# The instrument consists
of two carefully and accurately constructed clock movements, which are
driven by gravity and controlled electrically by the sidereal clock. The
movements revolve three type wheels. One of these turns once per second,
its edge is divided in 50 parts and it is driven by a separate movement.
The second wheel turns once per minute and the third once per hour and they
will print the seconds and minutes, while the first will give the
hundredths of seconds. A strip of paper is carried over these wheels and
moved forward by the same electro-magnet, which operat