#A1202. Comparator for Measuring Spectra Photographs, Scales, Etc.# Range 50 cm. The microscope travels on carefully straightened ways, and is moved by a screw of 1 mm. pitch. The screw head is faced with a silver band and is divided in 1000 parts. The handle for turning the screw is placed on the left side of the instrument so as to have the right hand free for recording readings. A set of change gears can easily be engaged to give a fast motion to the carriage. The stage will hold plates from 3 to 8 cm. in width and of 60 cm. in length. It can be shifted lengthwise for a distance of 25 cm. and is provided with adjustment for aligning the plates. The whole stage can be easily removed from the instrument. The microscope is fitted with variable magnifying power and is of standard size. Price #$450.00# #Note.#--The design of this comparator was suggested by Prof. Humphries, Director Laboratory of the U. S. Weather Bureau, for whom the first one was built. [Illustration: A 1203] #A1203. Comparator for Star Photographs#, measures in one direction 80 mm. and under right angle 60 mm. The lower part is constructed similar to our Comparator A1201. The top slide carries a divided circle for measuring position angles. The circle is arranged similar to a position micrometer. It is fitted with quick gear motion and tangent screw and the two verniers read to 1-100 degree. The microscope has variable magnifying power and is provided with reversing eye piece. This machine has been furnished for and is in use at Yerkes, Lick and Kirkwood Observatories. Price #$365.00# [Illustration: A 1204]