James E. Keeler, "The Spectroscope of the Alleghany Observatory. Offprint: Astronomy and Astro-Physics No. 111 (November 1893).  245x155mm, 11pp, 3 plates (of the instrument, plates numbered V, VI, VII). Original wrappers.  Condition: the pamphlet is in two pieces, the heavy paper plates I think were too much for the paper binding, and so it came apart in two parts at the plates. Also, there is an old vertical fold that runs through the publication.  But for that, a Good copy.  Not the best condition, but it is a rare thing. A nice contribution by a siginficant figure in teh history of modern astrophysics (see Donald E. Osterbrock, James E. Keeler: Pioneer American Astrophysicist: And the Early Development of American Astrophysics, Cambridge UP, 1984.  $100

"The spectroscope which is illustrated in the accompanying plates is the most important recent addition to the instrumental equipment of the Allegheny Observatory. Although not strictly a universal instrument it is intended to be used for several different kinds of work and to be efficient in all of them In a previous article f I have stated the general principles which must be observed in constructing a spectroscope for any given purpose It is not an easy task to design a spectroscope which shall satisfactorily meet a number of very different requirements and in presenting the Allegheny spectroscope as one solution of this difficult problem. I wish to point out that some additions and conveniences which might easily have been added were rejected because it was thought that they might compromise the utility of the instrument in some one of its applications. After testing the spectroscope in both visual and photographic observations although as yet only in a preliminary manner there are very few changes that I should wish to make in the original design. The instrument is large and powerful enough to compare favorably with others of the highest class designed for the same kinds of work yet light enough to be readily mounted and dismounted and to be carried by a telescope of moderate dimensions..."--from the offprint