74 



♦ KNOWLEDGE ♦ 



[Aug. 3, 1883. 



Whirlpool Rapids it is difficult to imagine. It was pro- 

 bably the exhaustion of his power among the rapids that 

 rendered the mighty swimmer unable to escape from the 

 whirlpool. We shall doubtless receive the accurate account 

 of the catastrophe in due time ; meanwhile, the recitals in 

 the English newspapers being more or less confused, I 

 thought an approximately accurate description of the scene 

 of the disaster might be of some interest." 



Before the event, I wrote as follows in the Neiecastle 

 WeeMij Chronicle : — " Captain Webb is more fitted than 

 most men to battle with surging waves, more practised 

 to maintain such actions as may give him the best 

 chance of safety ; but if he escapes his escape must 

 depend on a lucky chance causing his body — neces- 

 sarily inert to all intents and purposes throughout the 

 beginning of his course — to be carried towards the 

 whirlpool on the least dangerous course, and to be brought 

 under the surface only at intervals enabling him to breathe. 

 No one who has seen the Lower Rapids, and studied the 

 movements of the water there, can fail to recognise that 

 Captain Webb's skill as a swimmer will avail him scarcely 

 anything except at one critical part of his course, which 

 he may perhaps never reach alive. He himself clearly 

 recognises the risks he runs, though probably he has no 

 clear idea of the conditions under which he will be exposed 

 to them. Captain Webb's personal action in the experi- 

 ment will be akin to the influence of a drop of water on 

 the movements of a great roller in the Atlantic." 



The autopsy on Captain Webb's body showed that no 

 bones were broken. There was no wound sufficient to 

 cause death save one, three and a-half inches long in the 

 cranium. This wound was made after death. ^STone of 

 the symptoms of death by drowning were revealed, and it 

 was concluded that death resulted from the shock from the 

 force of the water in the Whirlpool Rapids coming in 

 contact with the submerged body with such force as 

 in.stantly to destroy the respiratory power, and, in fact, all 

 vital action. The shock was of sufficient intensity to 

 paralyse the nerve centres, partially dessicate the muscular 

 tissues, and forestall death by drowning. 



Ox the Hamburg tramways a number of cars with flange- 

 less wheels, much like omnibuses, and with turning gear, 

 are working. To run on the lines, these cars are fitted with 

 a shaft in front of the front wheels, this shaft carrying on 

 a lever a disc wheel which the driver can lower into the 

 tramrail groove as he requires, or raise it when it is neces- 

 sary to get out of the way of obstructions. The arrange- 

 ment works well, saves a lot of trouble, and the cars run 

 easier than those with flanged wheels. 



Messrs. Lamplugh i Browx, the well-known saddlers 

 of Birmingham, have recently brought out a new tricycle 

 saddle, which will be preferred by a number of riders to 

 any other saddle at present in the market. The leather is 

 suspended from the opposite ends of the saddle, and sup- 

 ported by a strong, flat, spiral spring, the tension of which 

 can be altered to suit the rider's weight, while ventilation 

 is provided far more efficiently than in any other saddle. 

 The leather seat is slightly cushioned, so as to provide a 

 soft surface to sit upon. At the back of the saddle there 

 is a small upright nickelised support, and in place of the 

 usual back-rest there is attached to this a solid cyclists' 

 wallet, which answers the double purpose of forming a 

 flexible back-rest for the rider and holding the tools, oil-can, 

 or any other small necessaries required on a tour. The 

 whole of the saddle is most ornamental in appearance, and 

 is tastefully got up as well as excellently made. 



LAWS OF BRIGHTNESS. 



TIL 

 By Richaed A. Proctor. 



ZOLLNER carefully observed the brightness of the 

 superior planets in mean opposition. His results are 

 as follows : — 



Prob. error 

 per cent. 



San = 6,994,000,000 times Mars 5-8 



Son = 5,472,000,000 times Jupiter 57 



San = 130,980,000,000 times Saturn (without rings) 5-0 



Sun = 8,486,000,000,000 times Uranus 6-0 



Son = 79,620,000,000,000 times Neptune 5-5 



It follows that, if the total brightness of Mars at mean 

 opposition is set at 1,000, as in my former table, we have 

 the following relative total brightness for the several planets 

 as observed, and as calculated for the case of smooth 

 spheres of equal reflective power : — 



observed Calculated 



Brightness. Brightness. 



JIars 1000 ... 1000 



Jupiter 1278 ... 487 



Saturn, without rings ..■ 534 ... 24'5 



Uranus 0824 ... 0-30 



Neptune 0088 ... 0058 



Zollner deduces for the reflective powers of these planets' 

 surfaces the values — 



Mars = 0-2072 Jupiter = 06238 



Saturn = 04981 Uranus = 06400 



Neptune = 0-4648. 



Zollner's observations of the moon at difierent phases 

 between the two quarters and full have next to be con- 

 sidered. It is obvious that as the diflferent parts of the 

 moon's disc, when " full," do not shine with the brightness 

 due to a smooth surface, we might expect to find her total 

 brightness at any other phase differing markedly from the 

 value estimated for the case of a smooth sphere. This 

 Zollner found to be the case. The " full " moon is far 

 brighter, by comparison with the gibbous moon (especially 

 when little more than half full) than the relation illustrated 

 in Fig. 10 would indicate. This relation is thus given by 

 Lambert for the moon assumed to be a smooth sphere. 

 Let V be the angular distance of the moon from the sun, 

 then the moon's total brightness varies as 



sin. V — i- cos. V 



After carefully analysing the whole subject, discussing 

 various hypotheses as to the moon's surface-contour, and 

 " averaging " as only a German philosopher can do, 

 Zollner treats the case finally, as though the moon were 

 covered with hills ha^nng a slope of -52° (it is not easy to 

 follow him on this point, for his formula does not corre- 

 spond to the case of conical hills, or prism-shaped hills, or, 

 in fact, hills of any shape with such a slope). But Zollner 

 is led finally to substitute for Lambert's formula the 

 following : — The moon's brightness, when she is separated 

 by an angle v from the sun varies as 



sin. {v - 52^) - {v - 52°) cos. {v - .52°). 



This formula cannot, of course, be actually correct, since 

 the expression vanishes when v = -52°, whereas we know 

 that the moon's brightness is not zero when she is 52 

 from the sun. As an empirical formula for the moon's 

 brightness when she is gibbous, however, it serves well, as 

 will be seen by the foUo-ndng table (where the brightness 

 of the full moon is taken as 100) : — 



