146 ANNUAL OF SCIENTIFIC DISCOVERT. 



SUBTERRANEAN PUOTOGRAPUY. 



A firm in Cincinnati have obtained the exclusive rijjht of takins: 

 views in the Mammoth Cave of Kontueky fi)r five years. The 

 process suecossfully used in takinj; pictures of the interior of the 

 Great Pyramid is adopted, usin;^ tl>t^ magnesium liglit. The 

 dampness of the cave, the smoke arisini^ in tiie consumption of 

 hirjre quantities of map^nesium, the diverjrency of tiie artificial 

 lijriii, and the majrnitude and proximity of th(^ ohjeets to be ph(j- 

 tojrraphcd, present a number of serious dilliculties. Powerful 

 rcilectors are used U) tiuow a Hood <jf ligiit upon tiie objei-t, and 

 the i)late is allowed about twice the exposure required by the 

 light of the sun. 



rUOTOGRArilING UPON SILK. 



A process has been devised at Lyons, France, for jihotograph- 

 ing upon silk, linen, etc., so that jH-rsons instead f)f mai'kiiig tlicir 

 initials upon the corner of a handkerchief, can have tlieir plioto- 

 graphs taken upon the fabric. In the silk shops, various articles 

 are exhibited, ]ihotogra])hcd with names, i)ortraits, and fanciful 

 devices. Tiie pictures are not injured by washing, and the pro- 

 cess is said to be easily aud rapidly effected. 



PllOTO-MICOGRAPIIY. 



Dr. J. J.Woodward, U. S. A., in a jiaper communicated to 

 " Silliman's Journal," for September, 1866, on the subject of jiho- 

 tography of microsco])ic objects, gives the following as the prin- 

 ciples involved: 1. To use ol)jectives so corrected as to luring 

 the actinic ray to a focus. 2. To illuminate by direct sunlight 

 jjassed tlirongli a solution of ammonio-sulphate of copper, which 

 excludes practically all but the actinic extremity of the spectrum. 

 3. Where it is desired to increas*; the power of any olycctive, to 

 use a i)r(jperly constructed achromatic concave, instead of iin 

 eye-piece. 4. To focus on plate glass with a focussing glass 

 instead of ground glass. 5. With high powers, to use a heliostat 

 to preserve steady illumination. 6. Where an olnject exhibits 

 interference phenomena when illuminated with parallel rays, as 

 is the case with certain diatoms, and many of the soft tissues, to 

 produce a proper diflusion of the rays by interposition of one or 

 more plates of ground glass in the illuminating pencil. Strict 

 adherence to these principles is indispensable to success. The 

 most powerful objective with which photographs have been taken 

 for the Army Medical JMuseum, was 1-50, made by Messrs. Powell 

 and Lealand of London. The subject selected for the experi- 

 ment was Pleurosifjma angulatvm ; with 1-50, and 3.| feet distance, 

 and without an eye-piece, a picture of a portion of a frustule was 

 obtained, magnified 2.344 diameters; this negative readily bore 

 enlargement to 19.050 diauu'ters ; the field in the picture is 6 

 inches in diameter, and is remarkal)ly sharp in the centre, but 

 shows considerable curvature, aud ou the edges is quite out of 



