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MINERAL PHOTOGRAPHY.

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By L. P. GRATACAP.

HOTOGRAPHY has accompanied man in al-
most every avenue of research.
It has even per-

formed an excellent service in psychology where, as in a realm of thought and emotion, it might hardly have been suspected of application. In the photographs of expression, abnormal facial states, of definite mental defects associated with physical features, photography has played a useful part. And it advances; methods improve and more and more skillful results are exhibited. Certainly in its artistic aspect the wonderful progress recorded in the last twenty-five years unfailingly shows how the operator becomes an artist. Delicacy and beauty, rich meanings and refined values of light and shade have been secured, its technique passing into the higher realm of artistry and composition.

How invaluable to science photography is: how in geography and travel its most obvious use has replaced the grotesquely misleading pictures of former days which were hand-made and served more to gratify the vanity of the illustrator than to inform the reader. In palæontology, in botany, in all branches of natural history its amazing power has been revealed. Since the invention of rapid plates and lightning shutters photography has conducted the investigator into new fields and in some cases, perhaps, has substituted its own harmless ordinance for the rapine of the rifle and the shotgun. What vast utility-which in its consequences assumes almost majestic proportions-has it not compassed in astronomy.

It is a pleasant problem to discover where photography— if applicable at all has not been helpful. In the mineral world there are temptations for the photographer and there are conquests to be made. To make a successful picture of crystals, to portray the fine needle structure of some zeolites to give character and definition to a specimen holding two or

three different minerals, to reveal the enclosures of transparent crystals, to make a mineral species speak from the picture of itself are tasks more easily discerned than solved, more easily bungled than finished. The writer responds to the kind invitation of the editor to contribute something to the ANNUAL, more from a desire to point out a field of work not yet adequately covered than from any conviction of his own that he has in this direction done any good work himself.

Some time ago he induced his assistant, Mr. Milton G. Smith, to undertake some experiments, and the results, chosen from a large number, are here shown. They are attractive, but it is quite incontestable that they could be excelled. Mr. Smith developed with ortol. He used appropriate backgrounds and manipulated the light. In this respect much of the secret doubtless lies. The possession of a room with many windows, the use of reflectors, the careful adjustment of the specimens to the light, a perfect control of the light by shades all go towards helping out, in fact are the indispensable adjuncts of successful photographs of minerals. And then the lens! There indeed is the deus ex machina of the whole business. The lens must have depth of focus and definition for at all commensurate work. This has been demonstrated over and over again, and Mr. Smith's equipment in this respect was not altogether adequate.

Some excellent photographs of minerals have been made under the direction of F. A. Canfield, the collector and mineralogist of Dover, N. J., and they were made with a superior lens. Ordinary lenses are of course greatly assisted by "stopping down" and long exposure, though in the latter respect gypsums, apophyllites, quartzes, and, generally, white and translucent or transparent minerals must not be too carelessly treated.

As I have before insisted a wide range of selection is offered in mineralogy of subjects, and more so than in almost any other branch of natural history since the variations of excellence in specimens is indefinite. It would be folly to waste time over poor specimens. But on the other hand the quality of some species is never high, and many have no photographic availability at all. One would like to see an album made up of quartzes and calcites, another of the zeolites, another of

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