80 



♦ KNOWL.EDGK ♦ 



[Ja\. 30, 1SS5. 



Ijeen put forn-ard in explanation of stellar aberration,* and 

 it may be alleged, with more than confidence, with the 

 fullest certainty of conviction, that no other theory can 

 explain the phenomenon. 



CHAPTER VII. 



TuE Earth's Motion as an Attendant on the Sun in 



HIS JOUKNET through SpACE. 



Since the stars are observed to be slowly .shifting their 

 positions on the celestial vault, and therefore presumably 

 in space, it is obviously suggested that the sun, whicli is 

 but a member of the sidereal family, has also his proper 

 motion through .space. It is a difficult problem to deter- 

 mine what that motion is, because all we have to judge by 

 is the movement observable among the stars, and, as the 

 stars are themselves in motion, it is not easy to separate 

 the effects of their own motions from those due to the 

 sun's. 



Still, this problem has been attacked and fairly van- 

 quished by as'.ronomy. It is true we cannot here get 

 certainty, because we no longer have absolutely certain 

 relations to deal with. But, as it is certain that, supposing 

 ihe Bun to be moving in a definite direction, there would 

 result a balance of stellar motions in the contrary direction : 

 we can obviously deduce the direction of the sun's motion, by 

 noticing the direction towards which the stars show the most 

 noteworthy balance of mytion. This has been done, and in 

 many ways. The result is that astronomers point confi- 

 dently to the constellation Hercules and its neighbourhood, 

 as including the point towards which the sun is speedin". 

 His rate of motion has been estimated at about 150,000,000 

 miles per annum, or between four and five miles per 

 second. 



I am only concerned here with the sun's proper motion, 

 in so far as it relates to the earth's motions. The con- 

 ception that the sun may be speeding through space with 

 this enormous velocity seems, at first sight, so contrary to 

 the fundamental hypothesis of modern astronomy, that 

 many persons have been led to believe there is a real con- 

 tradiction. They see that the earth's real path in space 

 can no longer be looked upon as a closed curve, yet Kepler 

 speaks of it as an ellipse ; that, again, the earth — according 

 to this new idea — is not travelling in a conic section, yet 

 Newton say?, all bodies under the influence of a central 

 attracting force, such as gravity, must move in some conic 

 section or other. 



In reality, however, there is no difficulty. Modern 

 astronomy only requires the earth and planets to move in 

 ellipses witlt, respect to the sun, not in space. Supposing 

 the sun at rest, and the planets moving in their present 

 ellipses around him, and that then under the action of far 

 distant suns, our sun began to travel through space, the 

 planets would not (as the paradoxer fears), be left behind. 

 They would be under the influence of those attractions as 

 well as the sim. They would obey them then, precisely as 



* I need take no further notice of a so-called explanation in a 

 work inirportiug to be written by a Cambridge wrangler (name not 

 given), than to remark that it does not even pretend to explain 

 details, and that what it does pretend to do suffices to exhibit the 

 utter ignorance of the writer as to the real nature of the problem. 

 I do not say that the writer is not a Cambridge wrangler, because I 

 know from my own experience that a man may become a wrangler 

 without knowing even the definitions of astronomy. But I do say 

 that the writer, being a wrangler, should have had sense enough to 

 know that before pretending to write on astronomy, he ought to 

 have acquired a better knowledge of the subject than he shows 

 himself to possess. 



he does, obeying all his influences as before. Thus their 

 motions, with resjKCt to him, would not be changed even by 

 a hair's breadth. 



The end. 



AN ELECTRIC TRAMCAR. 

 By W. Slingo. 



THE many experiments which have been made in 

 England, as well as in France and Belgium, to test 

 the applicability of electricity as a motive-power in place 

 of horses, have proved so little successful that one may be 

 pardoned for doubting the ultimate success of the movement 

 for many a long year to come. The long continued and 

 patiently pursued study of the question by the officers of 

 the Electrical Power Storage Company has, however, resulted 

 in what has every appearance of proving a success. 



It must be borne in mind that if there is a form of loco- 

 motion in which electricity has anything like a prospect of 

 being able to compete successfully with the present order 

 of things, that form is to be found in the propulsion of 

 tramcars. Here horses are almost the sole agent employed, 

 and, as everyone can see without any great stretch of 

 imagination, such an agent proves a highly expensive one. 

 In some districts steam has been, or is being, tried as a 

 substitute for horsepower, but while the expense is 

 certainly less, the accidents which have so far resulted from 

 the use of steam-propelled car.s have fostered and increased 

 a prejudice against them which is not likely to be speedily 

 overcome. Doubtless, with more experience on the part 

 of the drivers and other officers of the steam service, and 

 greater familiarity with it on the part of the public, these 

 accidents will be reduced to an insignificant minimum. 



An electrically- propelled car, if it is to become a com- 

 mercial success, must not only be capable of being worked 

 at a lower cost than is involved in the adoption of either 

 of the other alternatives, but it must be capable of doing 

 its work at least as efficiently and harmlessly. 



Whether or no these desiderata will be attained is, 

 of course, at present a matter of uncertainty, but in the 

 face of recent experiments there is every probability of 

 success being accomplished. 



The experiments in qiiestion have been carried out at 

 Millwall, at the works of the company above referred to, 

 and have been conducted by a very zealous and able elec- 

 trician, Mr. Reckenzaun. An ordinary car which has seen 

 good service on the London and Greenwich tram-line has 

 been procured, and, with but few modifications, has been 

 adapted to the new work. 



On the floor of the car, under the seats, are series of 

 rollers, and on these are run trays carrying a number of 

 secondary batteries of the latest and most adaptable pattern. 

 The front of the seat is boarded up, so that the batteries 

 are entirely hidden from view, and their total weight is 

 about 1 \ tons. The wires from these batteries are led to a 

 commutator, or switch, at each end of the car, so that by 

 turning or pulling over a handle the driver can apply or 

 withdraw the motive-power at will. The current from the 

 batteries is passed round the coils of one of Mr. Recken- 

 zaun's motors, which is placed under the car, and is not 

 seen unless looked for. The motor, which at full speed 

 runs at about 1,000 revolutions per minute, is geared on to 

 the axle of the driving-wheels, which are thus made to run 

 at about eighty revolutions per minute. The motor is well 

 covered in, whence there is little probability of its being easily 

 clogged with dust or mud. The weight of the motor and 

 gearing is about half a ton, so that the weight of the source 



