393 



KNOWLEDGE 



[Makch 10, 1882. 



those rc(iuiro to bo tlio host. The wholo \v(>iglit of tin- 

 ridor is thrown on those in liilinf^ up liill, and the friction 

 of Imdly Miailo bearings is very groat. 1 have soon such 

 liatl workmanship in the pedals of otherwise fairly-well- 

 inadu ninehines, that an ironmonger would have been 

 ashamed of such work in a set of the commonest kitchen 

 (ire-irons. 



At presi-nt there is only one good brake. Tiiis is a 

 riroular or semi-circular band of steel, whicli, by means 

 of a lever, can be made to clasp a drum. It is in a few- 

 instances, and should always be, applied by means of 

 two straps and drums and to botii wlieels. If one band 

 or drum were to give way in descending a hill, the other 

 would then suffice to prevent an accident. 



Great improvements have been made recently in double 

 tricycles, or, as they are generally called, Sociables. Last 



TIIK (IIJK.XT I'VKA.MID. 



JJy tiik Kditoii. 



WE have seen that the Great Pyramid is so perfectly 

 oriented as to show that astronomical observation! 

 of great accuracy were made by its archit<;cts. No 

 ostronomer can doubt this, for the simple reason that every 

 astronomer knows the e.xceeding difficulty of the task 

 which the architects solved so satisfactorily, and tliat 

 nothing short of the most careful obsi-rvation would have 

 enabled the builders to secure anything like the accuracy 

 which, as a matter of fact, they did secure. Many, not 

 acquainted with the nature of the problem, imagine that 

 all the builders had to do was to use some of those 

 methods of taking shadows, as, for instance, at solar noon 

 (which has to be first determined, be it noticed), or before 



The Pyinmiil Observatory, showing the object-end of the great observing tube. 



year the Sociable Salvo was the best machine of the kind, 

 but now the Premier Sociable is both lighter and a far higher 

 class of work. Machines of this kind, to c.irry two riders side 

 by side, need not weigh nearly double the weight of two 

 single machines of the same make. From being much wider, 

 they are safer than .-jingle machines, and they run lighter 

 than single machines when they are driven by two practised 

 riders. A better speed can be obtained on theui than on 

 a single machine. A good rider can carry a lady on the 

 seat beside him with very little assistance from his fair 

 companion. Indeed a problem has been proposed ; Given a 

 l.ady and gentleman driving a Sociable, to find the amount 

 of the pressure the lady puts on the pedals? 



But either with a lady or a gentleman, riding on a 

 Sociable is by most experts admitted to be the most en- 

 joyable form of this the most enjoyalilo of all sports. 



and after noon, noting when shadows are equal (which! 

 is not an e.xact method, and requires considerablel 

 care even to give what it can give — imperfect orientarl 

 tion), and so forth. But to give the accurtMjyl 

 which the builders obtained, not only in the orienta-l 

 tiou, but in getting the Pyramid very close to lati-l 

 tudo 30° (which was evidently what they wanted), only! 

 very exact obser\ations would serve. Indeed, if a moder 

 astronomer, knowing nothing about the Pyramid, were! 

 asked how the thing could be done without telescopic aid.I 

 he would be apt to say that no greater accuracy tlnxn (forO 

 instance) Tycho Bralie obtained with his great quadrant atl 

 Uranicnburg could have been secured. Now, the orienta-f 

 tion of the Great Pyramid approaches much closer toj 

 exactness than the best observations by Tycho Bralie with| 

 that justly-celeVirated instrument. 



