ASTRONOMICAL AND PHYSICAL INSTRUMENT WORKS.

JNO. A. BRASHEAR

Allegheny, Pa. ......................1890.

Objectives made from the same glass.

I presume you are aware that in this work, we are associated with Dr. Chas. S. Hastings, head of the Physical Laboratory of Yale University who is today at the head of mathematical optics in this country and his researches in the past two years have advanced our knowledge greatly in this line. Indeed our work is now entirely removed from empiricism and we can give the exact focus & corrections before the glass is made. Of course we make prisms of study for any objective.

The prices of our objectives in cells are as follows,--as per your request.

diagonal 15$ with one in. prism 18$ with 1¼ in. prisms. The prisms are all marked accurately plane and are of Jena Glass.

Our Polarizing Helioscope Eye piece is perhaps the best form made. It cost 50$ with ordinary form of bushing to fit telescope. If xtra bushing is needed, it is made at cost, ½in. face direct vision eye piece Spectroscopes 25$.

We make Telespectroscopes from 200$ (with diffraction grating or prism) to $2500.

We are just commencing on one of the finest spectroscopes yet, built for Prof. Chas A Young, Princeton Observatory, in fact we are now building nearly all the spectroscopes in the U.S. Have just completed the 2nd Spectroscope for Lick Obs. (we made the great Spectroscope) and we are now building beside the Princeton, a fine Spec'e for Carleton College Obs. & one for Vassar College Obs.

While I never solicit work–as it comes faster than I can do it–I am always glad to do anything I can for the furtherance of our beloved science, as a mere living figure. You know what wages means here so we cannot compete with foreign work in some particulars, but we can keep up the status of our work to the highest & so we never want for orders.  they are now many months in advance of us. I shall always be glad to give you any further information. Very cordially yours, J.A. Brashear.