The substance which he employed was the tungstate of calcium.  Taking crystals of this chemical compound, he spread the same over a cloth or paper screen, and used that screen to catch and convert the invisible images carried against it by the X-rays.  To his surprise, his experiment was completely successful.  All that is needed in this case is the cathode light, the object to be examined (as for instance the hand), and the screen treated with tungstate of calcium.  The observer looks through the screen, or into it, and sees with the unaided eye the invisible interior parts of the object examined, held between the screen and the cathode light.  The invisible rays take the image of the interior parts of an opaque object, and carry that image to the screen, where it is reconverted into visibility and delivered to the eye of the observer, without the aid of any instrument at all!  It is on this simple principle that Edison has invented his surgical and physiological lamp.  The announcement is that with this lamp the surgeon may look through the calcium tungstate screen and examine, for example, the fractured bones of the hand, and set them perfectly by actual inspection of the parts with his eye!

What then is the cathode ray?  At the present time its nature is not understood.  That it is a form or mode of motion goes with the saying—­unless it should be presently shown that all the imponderable forces are really material in their nature; that is, that they are an inconceivably fine and attenuated form of matter in varying manifestations.

The cathode rays are not light.  They are not sound.  They are not electricity or magnetism.  They are not heat.  They are not any of the known forms of force.  They seem to be a new transformation of some one or more of the known agents.  It has long been observed that motion is accompanied with sound, and that motion also, if increased, becomes manifest in heat.  It is known that heat is convertible into light, and light into electricity.

It is possible that at the bottom of all these phenomena lies the force of gravitation.  This force is absolute and universal.  All the others are partial and limited.  All the others, even the newly discovered cathode rays, are subject to obstruction by certain forms of matter; that is, to them certain forms of matter are opaque.  But gravitation knows no opacity in the universe.  No atom of matter is exempt from its sway.  It streams through all obstructive media as though such media did not exist.  It would appear that heat, light, electricity, sound, the cathode rays, and all other forms of force in nature are probably variations, and as it were limited expressions and manifestations, of the one supreme force that supports the constitution of the physical universe; and that one supreme force is gravitation!

Stages in Biological Inquiry.

THE NEW INOCULATION.