Science in Court.

Manufacturer and builder 7, 1876

How science may aid the ends of justice has over and over again been demonstrated, especially in criminal cases, where chemical analysis, photography, the microscope, and the spectroscope have often been resorted to for the purpose of shedding light on doubtful point, or even to give a final degree on which a righteous judgment might be based. Even in civil suits occasionally science steps in; this was beautifully illustrated in the suit now pending between Mr. Austin Black, the publisher of this journal, and the Continental Bank, for the payment of s cheek which Mr. Black had received in the course of his former business as a banker and broker, and which check was certified by the teller of the bank, but which certification the bank now repudiates as a forgery.

The testimony of the experts in that line was quite bewildering; these called for the defense giving reasons why they believed the signature forged, while those called for the plaintiff, among whom there were several bank-tellers and cashiers familiar with the signature of the teller of the Continental Bank, were emphatic in declaring the signature genuine.

Among the arguments brought for the defense that the signature was forged, was that it bore marks showing that it had not been written rapidly in an off-hand manner, as a man will do who has to sign his name many times during the day, but that it was slowly and elaborately drawn or painted. Another argument was that the blue ink was not of the same kind as that used on other checks signed about the same time at the bank. In support of this assertion, several other checks were produced, the signatures of which were acknowledged to be genuine, and which showed a different shade of color.

To set the first argument at seat, the check in question was photographed by W. J. Kuhns, that is, a negative was made from which a transparent positive was printed, and this placed in a magic-lantern or stere-opticon, when, by a powerful oxyhydrogen light, an enlarged picture of the check, with its signatures, could be thrown upon the wall. In order to exhibit this to the court, jury, and public, the court-room was darkened for a few minutes with black curtains prepared for the purpose, and the instrument, which had been kept in readiness, threw a picture of the check against the wall, in which the signature in question was enlarged to a length of some 10 or 12 feet, while the attorney for the plaintiff, ex-Judge Fullerton, called attention to the boldness of all the lines in the signature, which did not reveal the slightest hesitation, or were not wavering, as is always the case when a name is slowly written in imitation of a given hand-writing. The result here was quite the opposite from that obtained by the professor, described in Holland's story entitled "Sevenoaks," and which we reviewed in our late May number. The professor had a magic-lantern picture made of the supposed forged signature, and when its image was thrown much enlarged against the wall of the darkened court-room, it revealed a waviness of all the lines not existing in the genuine handwriting, which proved with certainty that it was a forgery. In this way a fact which otherwise could only be detected by a scrutinous eye, assisted by a magnifying-glass, was at once made patent to the jury and all persons in the courtroom.

As we said, the result in the case we are describing was the reverse; the lines forming the letters were bold and straight, and did not reveal the least wave or tremulous motion in the hand of the writer.

The second argument in regard to the ink was set aside by a spectroscopic examination made by Dr. Van der Weyde of the ink with which the signatures were written, and which showed that the signature in question was written with the same ink, and not with a different kind. As the principles on which this investigation is based may interest some of our readers, we will give here a few words more in explanation.

The chemist may use the spectroscope in two ways; the first end most common is to burn the substance to be investigated, when every elementary constituent will allow a peculiar set of luminous lines, exclusively its own and not belonging to any other substance, (details of this may be found on page 125 of our June number for 1871.) The second method is to use a complete spectrum of day, lamp, or gas light, oontaining all the colors, and to cause some of its color to be absorbed by the coloring matter to be investigated. Thus a pure red will absorb all the other colors but red; a pure green all others but its own; blue all but blue, etc. But it is founds that very few colors are pure; thus, for instance, some apparently pure reds contain orange, others violet, as proved by the fact that they do not absorb the orange or violet rays; some greens show the yellow and blue of which they are composed, while others absorb more or less of either, and only show the green part of the spectrum. So blue inks are made of indigo, anilin, Prussian blue, etc., and each of these coloring materials will show a difference in the absorbing power for different rays of the spectrum; thes the indigo will not absorb the red, but its absorption spectrum will show a wide blue and a narrower red line, the rest of the spectrum will be dark, while the Prussian blue will not show the red line at all, in fact It Is one of the purest blues we have, ultramarine not excepted, and when intense, it is the only color which darkens all the other colors of the spectrum, only leaving the blue unobserved.

When the colors are on paper, as in the case of a signature, the roughness of the paper, so much enlarged by the microscope, interferes somewhat with the observations, that is to say, sharp defined absorption bands can not be expected, but tho white spots in the paper make the band rough in outline, and show here and there colors in the dark bands; but the interference is by no means of such a nature as to prevent recognizing the similarity of two inks, and the dissimilarity of inks of different chemical composition.

The adaptation of the spectroscope to the microscope, under which various checks were examined, thud revealed the fact that the inks in all the signatures consisted of Prussian blue, and that the difference in shade in the check in question was not duo to a difference in the substance of the ink, but the commencement of a fading, very natural in a piece of paper which bad been handled and exposed to the light so much for several years as was the case with the check on which the suit is bated. Blue colors in general are apt to fade by exposure to light, as ladies and artists aro well aware: that exceptional blue which is not subject to this defect, is therefore called permanent blue, and of courses favorite color of paint, who are much interested in the permanency of their colors.