xo6 



NA TURE 



lULV 30. 1896 



milling these rays ; solids also conduct, though the conductivity 

 obeys different laws and only lasts for a short time. The 

 conduction through solids very closely resembles the phenomenon 

 called "electric absorption," a well-known example of which 

 s the residual charge of a Leyden jar. 



I have here some experiments which illustrate the effect of the 

 Riintgen rays on solids. In the first of these we have a lead 

 cylinder with a thin base made of aluminium. At the bottom of 

 the cylinder there is a thin layer of solid paraffin ; on the top of 

 this, and sticking to it, there is a large leaden disc, over which 

 paraffin has been |'>oured, so that the disc is entirely embedded in 

 the paraffin (Fig. 6). This cylinder rests on the aluminium window 

 in the iron chest containing the coil and the tube, this window 

 being very much smaller than the lead plate in the paraffin. I 

 now connect the lead plate to one pair of quadrants of a highly 

 charged electrometer, and then connect the two pairs of 

 quadrants together and with one of the poles of a battery of 200 

 small storage cells, the other pole of which is connected with 

 the iron chest, and so with the earth. I now disconnect the 

 quadrants from the battery, and then the quadrants from each 

 other. There is now very little movement of the spot of light 

 reflected from the mirror of the electrometer. When we turn 

 on the Rontgen rays, however, the spot of light begins to move, 

 and though the movement is small compared with that which 

 occurred in the experiment with air, it is quite decided. The 

 rapidity with which the spot of light moves soon, however, 

 begins to decrease, and after a short time becomes almost 



Tar/! PF(^^ 



To C o 1 u 



inappreciable. I now discharge the lead plate by connecting it 

 and both pairs of quadrants of the electrometer to earth for a 

 short time, then keeping one pair of quadrants connected with 

 the earth, and leaving the other connected with the lead plate, 

 we see that when the rays are off there is a very slight move- 

 ment of the spot of light in the opposite direction to the original 

 deflection; this is due to the leaking out of the "residual 

 charge." This movement is, however, greatly increased as soon 

 as the rays are turned on, and continues until we get quite a 

 large deflection; "the residual charge," or polarisation in the 

 paraffin, has then been enormously increased by the rays. The 

 conductivity of the paraffin under these rays resembles in its 

 properties that of the insulating sheath of a telegraph cable. In 

 testing the resistance of such a sheath, the current passing 

 through it does not remain constant, it rapidly falls ofl' in 

 intensity ; and if after the electromotive force has been applied 

 for some time it is removed, and the inside and outside of the 

 sheath connected with the terminals of a high-resistance galvano- 

 meter, a current flows through the galvanometer, and this 

 current is in the opposite direction to that which originally 

 flowed through the sheath. 



Ebonite shows the effect of the Rijntgen rays in increasing the 

 conductivity even better than paraffin. I have here a plate of 

 ebonite about I mm. thick, coated on both sides with tinfoil. I 

 put this on the aluminium window, and on the top of the ebonite 

 plate I place a lead disc, which is much larger than the aluminium 



window ; the object of this disc is to prevent the Rontgen rays 

 from striking against the wire connected with the disc, and so 

 discharging the disc through the air. That it is effectual in 

 doing this, is proved by there being no leak when the rays are on, 

 and the wire (raised to a high potential) disconnected from the 

 disc. If we now repeat with this plate of ebonite the experi- 

 ments we previously tried with the paraffin, we get similar but 

 decidedly larger re.sulls. I may mention that different speci- 

 mens of ebonite vary considerably in the magnitude of this 

 effect. There is one variation of the preceding experiments 

 which is of some interest. I will charge up the ebonite plate 

 without putting the Rontgen rays on at all ; on discharging, you 

 .see that the electrometer indicates that the "residual charge" 

 is coming out. I keep discharging the disc until the residual 

 charge is almost inappreciable. I now for the first time put on 

 the rays, and you see that the residual charge or polarisation, 

 which could not previously be detected, now becomes quite 

 marked. These experiments show how greatly the properties 

 of bodies are modified by the Rontgen rays, and show that by 

 their discovery physical science has received an agent which 

 promises to be of the greatest service in investigating some of 

 the properties of bodies which are now most urgently pressing 

 for explanation. 



LONDON UNIVERSITY COMMISSION BILL. 



T^HE second reading of the I^ondon University Commission 

 ■'■ Bill vvas agreed to by the House of Lords on Thursday 

 last. A full report of the debate upon the Bill was given in the 

 Times of Friday, and the following abridgement of it will show 

 the favourable feeling that exists for the appointment of the 

 Statutory Commission to deal with tlie reconstitution of the 

 University. 



The Duke of Devonshire moved the second reading of this 

 Bill. He said : As I made a short statement of the circum- 

 stances that have led to the introduction of this Bill when I 

 moved for leave to introduce it, it will not be necessary for me 

 to detain your lordships for any long time on this occasion. The 

 opposition to the Bill, of which I indicated the possibility, has 

 manifested itself in the form of a statement purporting to proceed 

 from two bodies entitled respectively the University Defence 

 Committee and the Gresham Commissioners' Scheme Amend- 

 ment Committee. It is not stated how those committees are 

 composed, and whilst I have no doubt that they fairly represent 

 those parties who are known to be opposed to legislation on those 

 lines, I do not think it will be contended that the body of opinion 

 which is represented by those committees can be compared for 

 a moment, either in weight or as regards scientific or educational 

 experience, with that body of opinion which in various ways has 

 given expression to its adoption of the principles upon w-hich 

 this Bill is founded. I think that in moving the second reading 

 it may be sufficient if I say that, in my opinion, the arguments 

 which are brought forward in this case do not establish any 

 reason why the Bill should not be read a second time. There 

 may be some points which are referred to in that case which 

 may be worthy of attention in Committee, and I think that 

 some of the statements may be eminently deserving of the 

 attention of the Statutory Commission if it should be appointed 

 under this Bill. Lord Davey has expressed his willingness 

 to accept the position of chairman of this Commission if it 

 should be appointed, and I trust that before the Bill leaves 

 your lordships' House, or at all events as soon as there appears 

 to be any possibility or probability of its being |)assed through 

 the other House, I .shall be in a position, in conjunction with 

 him, to state the names of those gentlemen who it is proposed 

 shall form the entire Commission. With this explanation I beg 

 to move that this Bill be read a second time. 



Lord Herschell : As I have the honour to be Chancellor of 

 the University of London, it is only natural that I should desire 

 to say a few words on the present occasion. The objections to 

 the measure may, I think, be put under two heads. It is alleged 

 that the scheme of the Commission of which Lord Cowper was 

 chairman, even when subjected to the scrutiny and modification 

 of the proposed Statutory Commission, would involve two con- 

 sequences — that it would lower or tend to lower the standard of 

 the degrees, .and that it would be unfair or tend to unfairness 

 towards those students who sought to obtain a degree without 

 having been connected with any college or collegiate instruction. 

 , The opponents to the scheme, both in the statement they have 



NO. i3q6, vol. 54] 



