The New Photographic Objective

Abstract

THE letter of Sir Howard Grubb in your issue of March 8 (p. 439) appears to make some further explanation desirable on my part. The invention of the new form of photographic objective seems to have been made about the same time in America and in England. An experimental lens of this kind was constructed by the Messrs. Clark, after consultation with me, in May 1887. The 13-inch lens which they subsequently made upon the same plan was completed on July 8 of that year. My absence during the summer in Colorado, with the intention of selecting a place for the new instrument upon some mountain of considerable height, caused me to overlook the account of the English invention in the Observatory. Since my return, the telescope has been mounted in Cambridge, on the grounds of this institution, where it is found to give highly satisfactory results. Photographs of eta; Orionis which have been made with it exhibit the elongation of the star, although the distance between its components is only about 1″. The newspaper report to which Sir Howard Grubb refers, that a patent was granted for the invention, is without foundation. The Messrs. Clark have never patented any of the improvements made by them in optics, and have had no intention of deviating from their usual practice in this instance.