724 



PHOTOGRAPHY, RECENT PROGRESS IN. 



cess, applicable to fabrics as well as to paper, is 

 another form of the diazo-type process. 



Prof. Newton recently offered a formula for 

 toning without gold, substituting nitrate of lead. 

 The chloride of silver gelatin emulsion paper, 

 first made by Obernetter, has become very popu- 

 lar by reason of the success with which it pre- 

 serves delicate detail and facilitates printing 

 from thin negatives. The carbon or anotype 

 printing process appears in many new formulas. 

 It is based on the insolubility of gelatin and an 

 alkaline bichromate after the action of light 

 The color of the image depends on the pigment 

 employed. The great value of carbon is in its 

 remarkable permanency. 



Rapid Photography. The net gain in the 

 rapidity of photographic action within the past 

 few years is not very great, but there have been 

 many useful and interesting advances in methods 

 of employing highly sensitive surfaces. The 

 experiments of Edward Muybridge in photo- 

 graphing animal motion, and the later experi- 

 ments of Anschiitz and others, have opened a 

 broad field of speculation and experiment in 

 movements looking to the use of the tachyscope 

 or similar devices for throwing rapidly success- 

 ive photographs upon the screen. The sugges- 

 tions of Edison and others as to the possible 

 co-operation of the phonograph and lantern 

 apparatus in transmitting to later generations 

 both the gestures and the voice of a speaker 

 have been based on proved conditions and possi- 

 bilities. The number of photographic images 

 necessary to the perfection of this scheme would 

 imply an elaboration of apparatus and a dupli- 

 cation of surface sufficiently great to render the 

 experiment exceedingly costly. Such a partner- 

 ship would imply some automatic union between 

 the two apparatus at the time the imp'ressions 

 were received, and the re-establishment of the 

 same automatic union at the time sound and 

 image were exhibited. 



Shutters or Exposers. The growth of rapid 

 photography is reflected in the enlarging num- 

 ber of camera shutters. The simple " drop- 

 shutter " form has been greatly and ingeniously 

 amplified. The disk shutter is widely used in 

 portable: cameras, as well as in pneumatic adjust- 

 able forms. There is much debate on the most 

 desirable shape of opening in transit shutters. 

 Many openings are made adjustable that the 

 exposure may conform to the conditions of the 

 exposure. Combination shutters, working with 

 both drop and flap or with crossing disks, are a 

 feature of recent inventions. One device pre- 

 sents an exposer opening in the center, enlarging 

 to the size of the lens, and closing to the center. 

 This, in many respects, admirable form has the 

 objection of giving the center of the plate the 

 greatest amount of exposure a tendency already 

 fostered by the natural action of the lens. An 

 effort to secure the exposure from the rim of the 

 lens toward the center is reported. The struct- 

 ural difficulties of such a movement are obvious. 



Artificial Light. The use of magnesium in 

 producing artificial light has been of great serv- 

 ice to photography. When properly used this 

 form of illumination has distinct advantages 

 over other forms. The " flash light " has great- 

 ly popularized social photography in the draw- 

 ing-room and at public gatherings, as well as in 



scientific and commercial channels. With the 

 flash light mines, caverns, and tunneled dis- 

 tricts are profitably explored. The flash pistol 

 or lamp has accompanied the police detective 

 into the opium den and the health officer into 

 the corrupting haunts of the tenement. It is 

 reported that at a gathering of civic and mili- 

 tary dignitaries on the occasion of the nine- 

 tieth birthday of the late Field- marshal Von 

 Moltke, Emperor William ordered a series of 

 flash-light pictures to be taken. The resulting 

 negatives were to be used in historical paintings. 

 Numerous incidents of the kind illustrate the 

 serviceable character of this artificial illumina- 

 tion. The value of the magnesium light in 

 portrait photography is now well established. 



Capt. Abney announces that magnrsium 

 burned in oxygen produces a light 12 times as 

 brilliant as magnesium burned in air. E. J. 

 Humphrey has burned magnesium wire in an 

 oxygen flask and, swinging the flask on the end 

 of "a wire or string, softened the edges of the 

 shadows. A platiaotype print was made by this 

 light in 55 seconds. 



Astronomical Photography. The progress 

 of this important department of photography 

 has been suggested from time to time in the 

 article ASTRONOMY. The partnership of the 

 camera and the telescope has immensely en- 

 larged the scope of astronomical research. The 

 orthochromatic plate has begun to play a part 

 in the survey of the heavens. Since 1887 the 

 astronomers of the world have been carrying 

 out the proposition of Dr. Gill, at the Inter- 

 national Congress in Paris, to make a com- 

 plete photographic map of the heavens. The 

 task of photographing over 20,000,000 stars 

 was divided among those observatories in dif- 

 ferent parts of the world which are suited by 

 position and equipment for taking up such work. 

 Ordinary telescopes, which bring to a focus the 

 visual rays, are not suitable for photographic 

 work. The superb Lick telescope, which lias 

 played an important part in the enterprise just 

 cited, is provided with lenses facilitating the 

 application of the camera. As Jerome Harrison 

 remarks: " The great advantage of the sensitive 

 plate over the eye in astronomical photography 

 is that the impressions produced upon it by light 

 are cumulative. The eye sees no farther into 

 space after gazing for ten minutes than it did in 

 the first minute ; but the effect of the light upon 

 the plate in such a case is 10 times as groat." 

 Thus this cumulative action of light on the 

 sensitive plate reveals stars and nebulae never 

 detected by the eye, even with the aid of the 

 most powerful telescopes. It has been estimated 

 that an exposure of one hour and twenty minutes 

 can reveal in the negative 400,000,000 stars. 

 Brilliant photographs of the moon are now 

 made in a fraction of a second. An extremely 

 small fraction of a second is sufficient in photo- 

 graphing the sun. Prof. Young estimates the 

 number of photographs of the transit of Venus 

 in 1874 and in 1882 at not less than 5,000. 

 Each succeeding transit is recorded by a greatly 

 increased number of photographic images. 



-In Other Sciences. Medical science ac- 

 knowledges a very considerable debt to modern 

 photography. Recent experiments with the aid of 

 the photographic medium include studies of the 



