SCIENCE 



[N. S. Vol. XXVIII. No. 727 



driven by tand or by a motor. Sparks from 

 four to eight inches long are taken from the 

 two terminals into parallel conductors having 

 high resistance. These resistances consist of 

 long, thin strips of cloth moistened with salt 

 solution. These lines spark to ground con- 

 tacts, which are about fifty feet apart, in the 

 yard outside. 



A thin wire is bent into a series of sharp 

 right angles. This wire may be looped into 

 either the positive or the negative line. 

 Photographic plates inclosed in hard rubber 

 holders are placed at these angles. Some of 

 them are exposed to the wire on the ground 

 side of the angle, and some on the machine 

 side. Their distance must be so adjusted that 

 they give symmetrical results when the spark 

 discharge around the angles is reversed. 



With the negative discharge the plates on 

 the ground side of the angles are much more 

 strongly fogged than those on the machine 

 side. Negative electrons having a mass of 

 about one one-thousandth of that of the hydro- 

 gen atom leave the wire at the angle, because 

 they can not turn the corner. They pass on 

 through the cover of the hard-rubber holder, 

 which maybe three sixteenths of an inch thick, 

 and fog the plate, which is developed in the 

 ordinary way. These particles have momen- 

 tum. They have energy of motion. They are 

 a component of matter, as is well established 

 by radio-active phenomena, and by well-known 

 electrical experiments. 



When the wire having these angles is looped 

 into the line from the positive side of the 

 machine this effect is also observed, but it is 

 very much feebler. With a cover to the 

 holders one sixteenth of an inch thick, 9,000 

 spark discharges in the positive line produce 

 about the same intensity of image as is ob- 

 tained with a single spark in the negative line. 

 And here the effect is vastly stronger on the 

 machine side of the angle than on the ground 

 side. The negative electrons are therefore do- 

 ing the work in the positive line also. They 

 flow through this line from the ground to the 

 machine. But they are not forced in under 

 pressure, as they are forced out from the ma- 

 chine on the negative line. It is these little 

 particles of negative electricity which consti- 



tute the electric current. They have kinetic 

 energy which they impart to the conductors 

 through which they are beating their way. In 

 an arc light they plunge across from the nega- 

 tive carbon to the positive carbon. Their im- 

 pact upon the positive carbon results in the 

 formation of a crater which is intensely 

 heated. About 85 per cent, of the light comes 

 from this crater in the end of the positive 

 carbon, which is, as has long been known, 

 more than 1,000 degrees centigrade, or 1,800 

 degrees Fahrenheit, hotter than the negative 

 carbon. 



In order to obtain the results here described 

 electrical oscillations must be prevented. This 

 is attained by means of the moistened strips 

 of cloth. When this has been accomplished 

 the sparks are large and brilliant at the nega- 

 tive end in both positive and negative lines, 

 and thin out towards the positive end. The 

 negative terminals are large spheres of about 

 10 cm. diameter. The positive terminals are 

 small knobs, of about 1 cm. diameter. While 

 on the large spheres the electrons repel each 

 other. But when they start into motion across 

 the spark-gap, they attract each other electro- 

 magnetically. This appears to be the reason 

 why the spark thins out as the electrons pro- 

 ceed in their motion across the spark-gap. A 

 " fat " spark is a sure indication of an oscil- 

 lating discharge. 



The fact that sharp shadow pictures are 

 formed of any thin object like a glass slide 

 lying on the photographic film imder the wire, 

 shows very clearly that these effects are due 

 to a cathode discharge. Whether or not X-ray 

 effects are also involved, is stiU an open ques- 

 tion. 



Arrangements are now being made to place 

 the angle-wire in a vacuum tube. This may 

 perhaps render these momentum effects visible. 



Francis E. Niphee 



SPINAL shock: a preliminary note 

 A PEW months ago, the writer, in con- 

 junction with Professors G. N. Stewart and 

 C. C. Guthrie, stated his belief that the cause 

 of spinal shock lies solely in the interruption 

 of the long conduction pathways of the spinal 



