The prismometric scale / by Charles F. Prentice.

  • Prentice, Charles F. (Charles Frederick), 1854-
Date:
[1891]
Catalogue details

Licence: Public Domain Mark

Credit: The prismometric scale / by Charles F. Prentice. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    THE PRISMOMETRIC SCALE. With Eleven Original Diagrams. BY CHARLES F. PRENTICE, NEW YORK. During the past two years “The Metric System of Number- ing and Measuring Prisms”1 has been a subject of considera- ble discussion, although the exact nature of its unit, the prism-dioptry, does not seem to have been generally under- stood, while its practical advantages to opticians, “of whom accurate work is expected,” have been wholly disregarded in some recent criticisms, in which it has been compared with Dr. Jackson’s and Dr. Dennet’s equally as scientific though less convenient systems. It is, therefore, now proposed to call at- tention to a still more simple feature of the metric system, with further explanations, yet with the understanding that the reader is familiar with its general principle and applications as originally explained. The prismometric scale, preferably drawn upon heavy paper or card board, consists of a line of gradations, “6 centimeters apart,”2 which are indicated by heavy vertical lines, with an in- o 3 4 5 6 7 8 9 io Index Line. Fig. i. dex-line at zero, longer than the rest, as shown in Fig. I, which JA Metric System of Numbering and Measuring Prisms. By Chas. F. Prentice. Archives of Ophthalmology, Vol. xix, Nos. I and 2, 1890, and Vol. xx, No. 1, 1891. 2See Archives of Ophthalmology Vol. xix, No. 2, 1890.