April 1, 1896.] 



KNOWLEDGE 



to 



to act badly, the spark illuminating the tube fitfully. 

 Then I reinstated the first one, and found it had renewed 

 its youth and worked as well as ever. Of course, until it 

 can be shown that the second improves with rest, one 

 cannot consider the point to be proved : it may be merely 

 that experiment has improved other conditions ; but for 

 those who have already spoiled their tubes, even the 

 possibility is cheering. 



It is exceedingly difficult to get a tube that will act. 

 Of the first five tubes of English make that I tried, none 

 gave good results. One cracked on being taken out of the 

 box — with no blow, but merely on exposure to the air of 

 the room. Another showed a white and violet light which 

 gave very little effect after very long exposures. A third 

 broke down at the first spark, owing to the air occluded in 

 the terminals being driven into the bulb and spoiling the 

 vacuum. The fourth and fifth are still intact, but appear 

 to require exposures of far greater length than any men- 

 tioned above. They are all much smaller than the old 

 Crookes tube, so I tried them with a small coil ; but 

 though they looked very pretty, they did little or no work. 

 It has been suggested that an aluminium window let into 

 the side of a tube would shorten exposure ; but the 

 difference in tone between a piece of glass and a piece of 

 aluminium electrographed on the same plate, was so 

 trifling as to show that the tube would not be worth the 

 trouble of making. An aluminium tube would be very 

 difficult to insulate. Other English tubes I have tried 

 give good results for a time. The mouse was done with 

 one which gave the proper green light, but which heated 

 so that it had to be worked a quarter of a minute at a time 

 and then have a quarter of a minute's rest, thus doubling 

 the time of the sitting. After three or four exposures it 

 deteriorated, the whitish blue light appearing instead of 

 the green, and a dark fatigue spot showing on the glass in 

 the centre of what had beeu the brightest ring of the green 

 light. As the tube deteriorated it gave the outline of the 

 object with about the same exposure, but it lost some 

 of its electrographic properties. For instance, the bones 

 of a sparrow hardly showed, whUe the feathers were indi- 

 cated, though not so clearly as in ordinary photography. 

 Other tubes gave varying results, but none showed any 

 sign of wearing for more than a few exposures. Of course, 

 if the current is carefully regulated they last longer. The 

 tubes now made are far smaller than my original Crookes 

 tubes, and I cannot help thinking that no great advance 

 will be made in this matter until some maker will give us 

 tubes of from four and a half to six inches diameter, 

 and as carefully finished off' as the original ones. Although 

 I should not expect anything from a tube with an 

 aluminium window, a mica one might give very much 

 better results, for mica is far more transparent to th) new 

 rays than glass. The focus tube now being talked of 

 seems to me a good idea, but I cannot consider it a novelty, 

 for the tube all my best early results were taken with is 

 one which has a concave cathode focussing on to a piece 

 of platinum in the centre of the tube, and is one of 

 Crookes' original make. To many my exposures will 

 seem inordinately long, but they represent the actual time 

 the sitter or object remained on the table, and take no 

 account of any waiting — treating a pause in the work as 

 exposure, which it practically is in a live subject. I do 

 not wish to boast, but hitherto I have never broken a tube. 

 Atmosphere makes a difference. A tube that had worked very 

 badly in a lecture-room overnight gave excellent results 

 next day in a sitting-room heated by a gas stove, which 

 thoroughly dried the air. 



The theory of this subject is at present very hazy. That 

 the phenomena arc due to electrical disturbance 1 have 



insisted on from the time I made my first successful experi- 

 ment. They seem to be the product of what is known as 

 the Hertzian ray, so called because it was first investigated 

 by a Swiss electrician, Hertz. A Hungarian professor 

 named Lenard forestalled many of Prof. Eontgen's experi- 

 ments, as the latter willingly acknowledges ; but to Prof. 

 Rontgen belongs the honour of applying the influence to 

 physiology. What its possibihties in that way may be no 

 one can yet foretell. 



It seems that the electrical waves are longer than those 

 of light, that they are propagated in straight lines, that 

 they are incapable of refraction, but not, perhaps, of 

 reflection, and are possibly not transverse but longitudinal 

 waves. To this last idea the researches of Lord Kelvin 

 lend colour. If this be so, before we can fully investigate 

 this set of phenomena we shall be in the difficult position 

 of having to divest our minds of all preconceived ideas 

 connected with the laws of hght. 



Hertz showed that the electrical wave can be propagated 

 by the ether without the intervention of what is generally 

 known as a conductor, much as the sound made by a 

 tuning-fork is given out by a violin string tuned to the 

 same note and placed at some distance off". The tuning- 

 fork gives out a simple fundamental note ; the violin string 

 gives out that note too, but, being fastened at both ends, 

 vibrates in nodes besides vibrating as a whole, and gives 

 rise to a host of overtones. For the tuning-fork substitute 

 the Crookes tube, and for the violin string substitute the 

 sensitive plate, and you have a rough and very imperfect, 

 but possibly helpful, analogy. It is not said that this is 

 what does occur, but merely that this helps the mind to 

 imagine what may occur. To carry the analogy further, 

 the electrical fundamental may be able to pass through 

 certain substances whicli the shorter actinic overtones 

 could not penetrate. When it gets to the photographic 

 plate, it may set up not only the electrical fundamental 

 but the actinic overtones which affect the plate. This is 

 a clumsy attempt to explain what no one as yet under- 

 stands. In an attempt to electrograph a sparrow under 

 chloroform a piece of cotton wool was placed on the 

 celluloid covering the plate and saturated with chloroform. 

 This came out quite black, whereas dry cotton wool shows 

 no more than feathers. In a further experiment to verify 

 this, some cotton wool saturated with water, some with 

 alcohol, and some with chloroform gave nearly similar 

 results, while a dry piece did not show at all on the 

 negative. This seems an added proof of the electrical 

 nature of the rays. The area of electrical disturbance 

 may easily be demonstrated by holding a smaU specimen 

 gaseous tube, such as is used in spectroscopy, near the 

 tube, coil, or cables, when it will be seen to glow at a 

 distance of several inches, just as it would if it were con- 

 nected to a battery. The region where it glows brightest 

 is near the negative pole of the coil. 



A paper on this matter would not be complete without 

 some allusion to Prof. ISalvioni's experiments in " seeing 

 the invisible." I took a funnel-shaped iron tube. On a 

 piece of black paper (such as is used for wrapping up 

 photographic plates) 1 gummed an area as large as the 

 large end of the tube. I allowed that to partially dry and 

 dusted it over with barium platino cyanide, using about a 

 drachm. This 1 attached to the iron tube by means of 

 elastic bands. When held up to daylight or bright gas- 

 light no ray of hght appeared, but when held near the 

 bright end of a vacuum tube a glow was seen, and a 

 purse held between the paper and the vacuum tube 

 showed distinctly a coin inside. The bones of the hand 

 show clearly through the tlesh, and the lead of a pencil 

 through the wood ; but the light seemed to me too dim to 



