It is curious to see that this expression of successive attitudes of the trunk and limbs, by means of a series of lines expressing the direction of the bones, has been precisely adopted by the ancient authors as being the most explicit and capable of making the phases of a movement understood. Thus, Vincent and Goiffon, in their remarkable work on the horse, have tried to represent by lines at different angles the displacements of the bones of limbs while taking a step.
It is not necessary to expatiate on the superiority photography has over actual observation for this purpose, giving the true positions of the limbs, while the eye is incapable of taking in such rapid actions in such short spaces of time.
At the commencement of this century the brothers Weber had recourse to the same mode of representation to explain the successive actions produced in the walk of a man. It was by reducing the walker to the figure of a skeleton that these eminent observers succeeded in presenting, without confusion, a number of images expressing different attitudes.
The method of constructing the bright metal bands which in the photograph explain the position of the joints, requires special mention. As the length of exposure is very short, a substance having great brilliancy must be employed. The strips of metal are not equally luminous down their entire length, because they do not reflect the solar rays at the same angle; they present lines of unequal intensity on the negatives. I have obtained the best results with small strips of black wood with nails having hemispherical bright metal heads driven in at regular intervals. Each little rounded surface reflected the image of the sun very brilliantly. In the photograph these lines of nails are reproduced as dotted lines. At the ankle, knee, and hip joints, nails of larger dimensions were inserted, showing these centers of movement by a much larger dot.
Partial photographs obtained by this method allow of the different acts of locomotion being analyzed, as well as the movements of walking, running, or jumping.
DETECTIVE PHOTOGRAPHY.
For several years Mr. D. N. Carvalho, the New York photographer, has made a specialty of the delicate use of photography which is brought into play more and more in connection with criminal cases in which disputed handwriting, forgeries, counterfeit money, etc., are features. The results now achieved are the outcome of years of experiment, and the photographic expert becomes in the end an expert in handwriting. Mr. Carvalho's gallery of records is an interesting illustration of what perseverance and ingenuity, aided by photography, can do toward solving apparently hopeless mysteries. To a reporter, who visited his studio, he said:
"We can do a great many things to bring the truth to light by the aid of photography. There is scarcely a case nowadays in which it is not brought into play if disputed handwriting is concerned. Of course the most famous case of late years was the Morey letter case. There is a photograph of the Morey letter up there in a corner. It yet remains a mystery, but we are certain that Garfield did not write it. I first found by photography that the envelope had been tampered with by the following process: Cutting the envelope open, so as to get a single thickness of paper, I put it between two sheets of plate glass, and placed it where the sun passed through it, the camera being placed on the shady side. Although no half-erased writing could be detected on the envelope with the naked eye or a glass, the difference in the thickness of the paper where erasures had been made showed plainly, as the light came through more clearly, and the erased words, which gave rise to so much discussion, were discovered.
"Below the Morey letter is a photograph of the signature of Alonzo C. Yates. Yates, you may remember, was a rich Philadelphia clothier, who, late in life, married a cook in the Astor House, and died, leaving a million or so to the wife. The daughters by a first wife disputed the signature to the will. I was employed by John D. Townsend to show the genuineness of the signature. We got thirty or forty genuine signatures of Yates admitted by both sides, and showed that a man never writes his name the same way twice. Then I took the signature of the will and another admitted by both sides, and enlarged them until each was 9 feet 4 inches long. The peculiarities of the writing became so apparent when shown upon that enormous scale—the signatures were so evidently by the same person—that the contestants gave up the case.