“Electricity in Vacuo” by Mr. T. Cuttriss.

The members of the Scientific Society and their friends had a most enjoyable and instructive evening on Wednesday the 24th November, when Mr. Cuttriss gave a lecture and demonstration on the wonderful advances that have been made in electrical science during the last few years; especially with regard to the behaviour of electric energy in glass tubes from which the air has been exhausted to a greater or less degree.

Beginning with a description of the Storage Battery and its uses, Leyden Jars, etc., the lecturer went on to show that when the electrical spark is made to pass through a partial vacuum its length is greatly increased, and many other phenomena take place of which until lately the scientific world had no knowledge. Experiments were shown illustrating the action of the electric spark in the open air. When the terminals of the coils of the battery are brought near each other a bright spark passes from one terminal to the other, accompanied by a loud report. This is, in fact, lightening and thunder in miniature. The spark will pass through a sheet of card held in its path, making curious torn punctures in the card, the frayed edges of the holes being equal on both sides of the card, as if an explosion in the card itself rather than from the passage of something through it. After having mentioned the New Telegraphy, without wires, the lecturer promulgated the theory that “Electricity is a Wave Motion of Ether.”

Proceeding to the subject of “Electricity in Vacuo,” a number of experiments were shown with tubes of various degrees of exhaustion. These tubes consist of long glass cylinders from which the air has been extracted, and into each end of which is fixed a wire for connection with the coils of the battery, and which is known as an electrode. It was shown that a spark gap, in air of only a few inches, was increased in the tubes to the whole length of the tube. Further, it was seen that the condition of the spark varied to the amount of exhaustion in the tubes. In the first, of moderate exhaustion, a thin bright line of light passed from electrode to electrode.

On greater ramification of the air, the light becomes defused, until finally in the tube of greatest exhaustion the light fills the whole tube with a lambent glow. In this condition the light frequently appears to be cut transversely into a series of rings with less luminous intervals between them. When the exhaustion has been carried to the one-millionth of an atmosphere, the appearance of light diminishes, the spark does not pass so far, and the whole tube gives a pale luminosity 

The Geissler Tubes were then exhibited. These consist of double tubes, one, which is coiled and exhaustive being within another, a liquid substance intervening between the inner and outer tube. By these tubes the spark gap may be greatly increased, a gap of about 2 inches in air passing through 24 feet of Geissler Tube. The illuminated Geisser Tubes have an exceedingly beautiful appearance and were greatly appreciated by the audience. – Professor Crooks, after numerous experiments with vacuum tubes and the phenomenon exhibited by them, propounded his theory of “Radiant matter.” He supposes that when exhaustion in a vacuum tube has gone to one-millionth of an atmosphere, molecules of residual gas have a free path in which to move about without striking each other sufficiently to produce a visible glow. At this stage the molecules are strongly attracted to the cathode or negative electrode. Then having been negatively electrified they are thrown off with great force and unless interrupted by some solid body will strike against the sides of the tube, and cause the characteristic fluorescent glow. This radiant matter is generally known as the Cathode rays.

Various modifications of Crooke’s Tubes were shown, and experiments of a very interesting nature were carried out. In one tube was a small wheel, like a waterwheel, and when the electrodes were connected to the battery the rays caused the wheel to rotate, but on deflecting the rays by the action of a magnet held near the tube, the rotation was reversed, the wheel being converted from an over-shot to an undershot wheel. The deflection of the cathode rays by the magnet shows that they are not light, whatever else they may be. In another tube were some crystals of an ore of Tungsten, and when the rays were turned on to these crystals they glowed with an intense ruby light, although there was no appearance of light falling upon them. – Another application of electricity in vacuo was shown in the Arc electric light.

The lecturer then passed on to what was probably thew most interesting part of a very interesting lecture. To wit: “The Roentgen Rays.” It was in December1895, that Professor Roentgen, while experimenting with vacuum tubes, discovered that certain bodies were rendered fluorescent, by something which emanated from but was not visible. Leonard, an Hungarian physicist had previously observed something of a similar nature, but Roentgen first succeeded in photographing the bones of a living hand, and so called general attention to these wonderful rays which bear his name, though he preferred to call them X Rays.

Further experiments have resulted in the invention of the Florescent Screen for receiving the rays. This screen is composed of Potassium-platino-cyanide, and in appearance is like a child’s drawing slate. If an object be placed between the Roentgen tubes and the screen, an image of the object is cast upon the screen, and many substances quite opaque to light are traversed by the rays, while other substances transparent to light do not allow the rays to pass. Metals generally are not rendered transparent, but aluminium is an exception to the rule. The nature of these X Rays is still sub-judice. They are not light, for they will not pass through glass, and will through wood, etc.

They are not Cathode Rays, for they are unaffected by the magnet. They appear to be generated in the Roentgen tube, where the Cathode rays impinge upon a platinum disc, and hence they are reflected and pass out of the tube. Possibly they also are radiant molecules of a nature from those of the Cathode rays.

A number of radiographs were exhibited, and many opaque objects were shown to be rendered transparent by the rays. Among other objects was shown the hand of a man who was lately shot, and whose case it will be remembered was lately in the County Court. When he placed his hand between the tube and the florescent screen, the bones of the hand were clearly visible, and numerous dark spots in and among them representing the pellets which are embedded in the flesh of his hand. 

These experiments with the Roentgen rays concluding one of the best evenings that the Scientific Society had had.”