March 13, 18S5.] 



KNOWLEDGE 



210 



Fig. G. The Lifting Pout-oou and Railway Cradle 



her back would be broken in the first big seas she 

 encountered. Comprehending this, the designers of the 

 ship carriage make its strength reach its maximum in the 

 cross girders, which are spaced like the lateral lines cf the 

 rams already described ; that is to say, seven feet apart, 

 and hiving sufficient depth and material in their plates to 

 ensure an equal deposit of weight upon all the wheels. 

 These latter are doub'e flanged, and are placed close to- 

 gether, each being hung independently on its own journals, 

 and having its own axle. Under an ordinary railway car 

 the four or tix- wheel trucks move together aVjout a central 

 pin. But in the ship carriage, which is not designed to 

 move oflT f rom an almost straight line, this is not required, 

 and greater strength is obtained by adhering to the rigid 

 principle ; elasticity being had by placing a powerful spring 

 over each wheel. These springs will, as said before, bear 

 a weight of twenty tons and have a vertical movement of 

 about eLx inches, while the maximum weight they will be 

 called upon to bear will not depress them more than three 

 inches, and allow for crossing irregularities without bring- ■ 

 ing an undue weight upon the wheels. 



There is also a system of supports for the vessel, each 

 having adjustable surfaces hinged to the top of the sup- 

 ports by a toggle-joint in such a way that they miiy bn 

 made to closely follow every depression, and yield easily to 

 every protuberance or bulging. They pierce the girders of 

 the carriage, and are exactly pendent over the hydraulic 

 rams when the carriage is on the pon'oon and rests in its 

 proper position. Thus, as will be seen, the ship, wl.en 

 crossicg the Isthmus (see Fig. 1, ante), rests upon what 

 might be cilled a cu.shion ; and, indeed, she will have expe- 

 rienced far rougher treatment, both in the Atlantic and 

 Pacific, under ordinary conditions of weather, than that 

 had while in transilv. by rail across the Isthmus. 

 (To he continued.) 



(S'ijitovinl (gosfSfp. 



For some reason best known to himself the compositor 

 has entirely suppressed the ij which I wrote before 

 the words " Ursa? Majoris," in the third paragraph of 

 " Editorial Gossip " on p. 200. 



Ox the evening of this day 104 years; in other words, 

 on that of March 13th, 1781, an eighth body was added 

 to the solitary seven (including the sun and moon) of our 

 system with which mankind had been acquainted from pre- 

 historic times ; for this is the anniversary of the discovery 

 of Uranus by Sir William Herschel. Not that he was the 

 fiist observer who detected the planet (which, as a niattev 

 of fact, at and about the time of opposition, is visible to 

 the naked eye), inafmuch as it had been previously ob- 

 served, and its position noted, once by Bradley, five tiuieo 

 by Flamsteed, once by Meyer, and actually twelve times by 

 Le Monnier, who would certainly have discovered its 

 planetary nature had he only compared three of his own 

 observations of 17C5. It may serve, however, to give an 

 idea of the care and method of the French astronomer if I 

 recall the fact that Arago saw one of his observations of 

 Uranus written on a paper-bag which had contained hair- 

 powder ! It is, further, instiuctive to note that had the 

 great astronomer of Slough turned his telescope upon the 

 planet on JIarch 2nd, instead of on the 1.3th, he must 

 have failed to detect its character from its motion, it 

 havii.g been at one of its stationary points in the heavens 

 at the former date. Upon such trifles may great dis- 

 coveries hinge. How Herschel himself named his addition 

 to the solar system the Georgium Sidus, as a conipliineut 

 to his patron, poor mad George the Third ; how Lalande 

 strenuously endeavoured to affix the name of Herschel 



