336 SUMMARY OF CUERENT RESEARCHES RELATING TO 



the Abbe diffraction tbeory, a translation of the author's treatise 

 would, we feel sure, have been of benefit to English readers. It is 

 divided into three parts, the first dealing with diffraction, the second 

 with aperture, and the third with the relation of aperture and power. 



There are some terse passages on the aperture controversy of , 

 1881, and the part which this Society took in finally elucidating the 

 question, one of which we reproduce, though as we do not desire to 

 fan into a flame again any of the slumbering embers of the old fires 

 — if, indeed, they are not extinct — we leave the passage in its original 

 Spanish. 



"La nueva teoria — la verdadera — sobre la vision microscopica, 

 es aiin muy poco conicida. A pesar de que su origen data de 1873, 

 y de haberse dado cuenta de ella a la Eeal Sociedad de Microscopia 

 de Londres en 1877, su conocimiento no se difundio mas alia de un 

 circulo muy pequeno ; y apenas era conocida en Alemania, Inglaterra 

 y los Estados-Unidos de America — paises en donde la microscopia se 

 encuentra en floreciente estado — antes de 1881. Desde esta epoca, 

 su conocimiento ha empezado a extenderse ; y de la lucha entre los 

 partidarios de las antiguas y modernas teorias, ha salido victoriosa 

 en terminos tales, que hoy nadie se atreve a disputarle el triunfo. 

 Mr. Shadboltj el mas decidido adversario de la ' Teoria Abbe,' y el 

 que, con mas vigor le ha hecho la guerra en la Eeal Sociedad de 

 Microscopia de Londres, ha tenido que darse por vencido, y nada en 

 contra ha vuelto a publicar (que yo sepa a lo menos) desde 1881." 



Fine Platinum Wire and Thin Gold Leaves.— Mr. H. T. Eead 



is said * to have made some wire so fine that it is too thin to be seen 

 with the naked eye, though it can be felt. A platinum wire is made 

 the core of a silver tube, and then drawn out with the silver to the 

 thickness of the original platinum wire. This is in turn made the 

 core of another silver tube and again rolled out, and, finally, the silver 

 is dissolved off with nitric acid. It is intended to use this wire as a 

 substitute for spider-webs. 



Mr. A. E. Outerbridge,"!' by electro-plating a known weight of 

 gold upon one side of a sheet of copper-foil of given dimensions, 

 obtains a coating of gold upon the copper whose thickness is readily 

 ascertainable by a simple calculation ; then, by using a suitable 

 solvent, the copper may be removed, when the leaf of gold will 

 remain intact. After a series of careful experiments he has obtained, 

 in this way, sheets of gold, mounted on glass plates, which are not 

 more than 1/40,000 mm. thick ; and has some specimens which he 

 has good reason to believe are not more than 1/400,000 mm., " about 

 the 1/200 part of a single wave-length of light." 



* St. Louis National Druggist, vii. (1885) p. 308. 

 t Amer. Mon. Micr. Journ., vii. (1886) pp. 37-8. 



