Experiments with Cathode Rays

Professor Pupin Obtains Gratifying Results in the Laboratory of Columbia College.

SEVERAL GOOD PICTURES.

The Bones of a Hand, Nails in a Box and the Cogwheels of a Watch Faithfully Reproduced.

HINTS FOR EXPERIMENTERS.

In the laboratory at Columbia College yesterday afternoon Professor M. I. Pupin, the professor of physics of the institution, continued his experiments in the photographing of invisible objects on the lines laid down by Professor Roentgen, already explained in the HERALD, and obtained very gratifying results. There were many students of the college present while the Professor made his experiments and explained the various phenomena as fast as they developed, and all were most deeply interested in them.

The first photograph taken by the Professor was of the hand of one of the attendants of the college. The picture was excellent and showed the bones and joints of the fingers and of the body of the hand very clearly, the flesh appearing on the plate like a filmy shadow.

Next, the Professor put some nails in an aluminum box, focused the rays from the Crookes tube upon it, and in a short while had a picture of the nails in all their details nearly as faithful to the originals as if they had not been enclosed in a box.

A NEW PHENOMENON.

The students were surprised and greatly interested, but more so when the Professor photographed the cog wheels in the works of an aluminum covered watch. Many other objects were photographed with equally gratifying results, and while the Professor was engaged in making his later pictures, he noticed a fact that struck him as very queer and that was that an underexposed picture of a hand did not show the bones at all. The explanation of this phenomenon the Professor will try to study out.

In speaking later of his experiments and of the use of Crookes tubes in the photographing of invisible objects, Professor Pupin said the whole thing was very simple and that the only difficulty lay in getting the correct apparatus and in making the pictures under favorable conditions. Crookes tubes are very expensive, and for that matter they are very scarce also, so scarce, in fact, since scientists began photographing the invisible with them, that dealers in the tubes have been forced to cable to Europe for a full supply of them.

As Professor Pupin said, if he could have got a Crookes tube several days ago, Columbia College would have had the honor of making the first photograph in this country of an invisible object. Such tubes as he used, he said, he had prepared himself.

CROOKES TUBES VERY EXPENSIVE.

Professor Pupin said the reason Crookes tubes were so expensive was that they broke easily, because of the heat of the electrodes. It was very important, therefore, he said, for all using the Crookes tubes to carefully watch the electrodes all the time, and to cut the electrical current off the moment they began to sputter, as this was a certain sign that the intense heat would crack the glass, permit the air to enter the tube, and, naturally, break it, and thus force the experimenter to go to the expense of buying another.

In the course of his experiments the Professor used tubes without electrodes, simply wrapping tinfoil on the outside of them, and found they gave results quite as satisfactory as those obtained from tubes with electrodes. He found, too, and that was an important item, that tubes with the tinfoil didn’t break. However, they necessitated a longer exposure of the object to be photographed, but the Professor did not think that a serious objection, in view of the satisfactory results obtained.

The Professor said to me that this matter of photographing the invisible had been thoroughly discussed and established as a fact and that, as far as known now, there was nothing novel in it. The next step in the development of it would be to make instantaneous photographs, and he believed that would yet be done. As it is now an object has to get a long exposure to the sensitized plate before it can be photographed.

SURGEONS INTERESTED.

At the College of Physicians and Surgeons, in West Fifty-ninth street, Professor Roentgen’s way of photographing the invisible has excited the deepest interest on the part of professors and students, and Dr. George S. Huntington, the professor of anatomy of the institution, has taken the matter up with his characteristic vim.

As yet Dr. Huntington has not made any experiments at the college, as the electrical appliances there do not give out a sufficiently high voltage, but, it was stated last evening, such experiments as he may make will be made in conjunction with Professor Pupin, in the laboratory of Columbia College, in East Forty-ninth street.

The desire to photograph the invisible is not confined to Columbia College alone of all the educational institutions in this city. It has spread to the University of the City of New York and also to the City College, where professors and students alike, figuratively speaking, have it on the brain. At the City College it was said some experiments were tried yesterday, but without satisfactory results, as the Crookes tubes broke.

Nikola Tesla is still experimenting in the same direction as the others, but is using his own tubes. He does not feel at liberty, he says, to state just yet what results he has obtained.

The wizard Edison regards the results he has thus far obtained as slight, but hopes for fully satisfactory ones as soon as his new apparatus is made.