August 5, 1897] 



NATURE 



317 



material nature of the rays, and the only novel point in the 

 paper referred to seems to me to be that the rays owe their 

 greater or less penetrative power to the fact that they are par- 

 ticles less or more free from electric charges. If this were the 

 case, it seems scarcely possible that the particles could pass as 

 freely through, and in the neighbourhood of, a conductor when 

 charged as when uncharged. If the particles were completely 

 without charge, it is true they should be equally affected by a 

 conductor first charged positively, and then with an equal 

 negative charge. On the other hand, if the particles were 

 positively charged, they would experience stronger attraction 

 to a conductor negatively electrified than to the same conductor 

 equally positively charged ; and the same, mutatis mutandis, 

 may be said if they are negatively charged. 



The effect one might expect is that the uncharged particles 

 would at first be attracted by a charged conductor, and then 

 repelled from it, if they acquired part of its charge, in which 

 case the photographic image of the uncharged conductor pro- 



tduced by the X-rays would be modified in intensity if not in 

 form ' — probably in both. 

 If, as Messrs. Vosmaer and Ortt suppose, the " rays " are 

 diselectrified by striking against the charged anode inside the 

 tube, it is difficult to see why they should not be re-charged, and 

 therefore act like other charged particles, if they strike against 

 an electrified conductor outside the tube, especially if the 

 \ potential of the external conductor be as great or greater than 

 ' the potential of the internal. Indeed, the authors of the paper 

 admit this ; and if it is true, one might reasonably expect some 

 such action as I have sought for. 



I therefore thought it would be, at any rate, worth trying 

 experiments to see if the X-ray jihotograph of a conductor, 

 such as of a small plate of aluminium (with carefully rounded 

 edges), differs according to (i) whether it be charged or not, 

 and (2) whether it be charged positively or negatively. 



According to the paper the X-ray particles are to be con- 

 sidered free from charge when they completely discharge a 

 charged insulated plate, without afterwards imparting to it a 

 charge, and the focus tube I used in all these experiments was 

 one which gave rays of this description. 



In the first set of experiments two small squares (A and B) 

 with rounded edges, cut from the same piece of sheet aluminium, 

 and one-thirtieth of an inch in thickness, were arranged in the 

 same horizontal plane beneath the focus tube placed sym- 

 metrically with respect to the anode of the tube, so that the 

 line joining the centres of the squares was in a direction at right 

 angles to the line joining the centre of the anode and the centre 

 of the kathode mirror. Below these small squares, and resting on 

 a thick block of paraffin, was placed the photographic plate (all 

 the plates used belonged to the same batch — the Ilford special 

 rapid, and all the plates of each set of experiments were de- 

 veloped together in the same dish). The tube was worked by a 

 large coil, giving six-inch sparks, and A and B were electrified 

 when necessary by wires from the poles of a Wimshurst machine 

 with leydens giving seven-inch sparks between the nobs when 

 used in the ordinary way. The duration of each exposure was 

 timed by a stop-svatch in each case, and was as nearly as pos- 

 sible the same for each set of experiments. 



A blank experiment in each set, in which the plate, wrapped 

 in dark paper (the same number of folds in every case), was 

 exposed to the radiation from A and B without the Rontgen 

 rays, proved that no photographic effect was produced by their 

 electrification by the Wimshurst. 



Exposures were then made as follows : — 



(1) A and B both earthed by a wire soldered to a gas-pipe. 



(2) A positively, B negatively electrified. 



(3) A negatively, B positively electrified. 



(4) A positively, B to earth. 



(5) A negatively, B to earth. 



(6) A and B both earthed. 



Development showed that the electrification of A and B was 

 without effect, either absolute or comparative. 



Since in the above experiments sparks passed between A and 

 B when their difference of potential exceeded an amount far less 

 than that which could be given by the Wimshurst, and it seemed 

 possible that a stronger charge might still yield some indication 



1 The alteration in form, and to a certain extent intensity, would depend 

 partly on the velocity with which the particles were travelling. I do not 

 remember reading of any determinations of the velocity of prop.\?ation of 

 the X-rays ; but if this remains very high over great distances, .as it 

 seems to do, it would appear very unlikely that the rays consist of material 

 particles. 



of a difference, one of the aluminium squares was removed, 

 and the other shifted till it was immediately beneath the anode, 

 and a second set of experiments was made in a rather different 

 way. In each pair of exposures the same plate was used, each 

 half of the plate being protected, whilst the other half was ex- 

 posed by a thick slab of plate glass— proved by experiment to 

 allow no developable action of the X-rays to pass through it 

 during the time of exposure used. The experiments were as 

 follows : — 



(i) A blank experiment without the X-rays in which one-hall 

 of the plate was exposed, first to A charged positively to the full 

 power of the Wimshurst, and then the other half to A charged 

 negatively in the same way. The result showed there was no 

 developable action. 



(2) 1st half X-rays only, then an interval of rest (the same 

 interval being allowed between every experiment), then the 2nd 

 half to the X-rays only ; this was done to see how the emission 

 of the tube varied. 



(3) 1st half A positively charged, 2nd half X-rays only : A to 

 earth. 



(4) 1st A negatively. 2nd A to earth. 



(5) 1st A positively. 2nd A negatively. 



(6) 1st A insulated. 2nd A to earth. 



(7) Same as (2). 



(8) Same as(l). 



The whole of this series was repeated, using the contents of 

 one box of Edwards's isochromatic plates. Development 

 showed no action which could be attributed to the electrification 

 of A. 



In a third series of experiments A was connected by a wire 

 first to the kathode loop and then to the anode loop of the focus 

 tube, and radiographs were taken comparing the effects of this 

 treatment with that of earthing A ; but these, too, gave no indi- 

 cation of any increase or decrease of the X-rays reaching the 

 plate, nor of any re-distribution of the rays. 



In a fourth set the photographic plate was placed on an 

 ordinary discharging table, and brush discharges, and afterwards 

 thick sparks were passed between the poles of the discharger, 

 and the radiographs developed ; but they showed no traces 

 whatever of any effect of the sparks. 



I, therefore, conclude that the radiograph of a conductor 

 (though it is true I have only tried aluminium and brass) is not 

 sensibly altered by even powerful electrification, nor are the rays 

 altered in force or direction in passing through air in the neigh- 

 bourhood of a powerfully- charged conductor, nor even through 

 air which is being subjected to a powerful disruptive discharge. 



This seems to me to make it more difficult to believe that the 

 X-rays are due to particles, whether totally or partly devoid of 

 charges of positive or negative electricity. T. C. Porter. 



Eton College, July 5. 



NO. 1449, VOL 56] 



Primitive Methods of Drilling. 



In Nature for June 10 (p. 140) there was an abstract of a 

 monograph upon drills, dealing, among others, with those used 

 in ancient Egypt. May I be permitted to point out that the 

 object shown in Fig. 3 is not, as the author suggests, a drill 

 bow, but a censer. 



Again, the meaning of the sign saiii (explained by Mr. 

 McGuireas a disc drill), when used as a phonetic hieroglyph, is 

 perfectly certain. It means "joining" or "union," and when 

 accompanied by the lotus and papyrus (called "strings" by the 

 author), "union of Upper and Lower Egypt." The figures 

 accompanying it are most certainly gods, and not captives. At 

 the same time, the sign sam occurs as a determinative to the 

 word casanet, usually translated chisel, but which may well 

 mean a drill such as Mr. McGuire indicates. 



Constantinople, July 10. Franz Calice. 



Meteor of July 29. 



In case it may be of any interest to you, I beg to inform you 

 that at 7.45 p.m., yesterday (Thursday, July 29), when standing 

 0° 29' 40" W., by 51° 10' 12" N. (Sparelands or Willinghurst on 

 I -inch Ordnance Map, Sheet 285, near Cranleigh) I saw a 

 meteor fall in a direction bearing 46' east of north, as near as 

 I could tell by a bearing subsequently taken. Its appearance 

 was that of a falling magnesium star rocket. It did not appear 

 to explode, but left a long trail of fragments. 



Willinghurst, Gui'dford, July 30. J. V. Ramsden. 



