Mat 29, 1885.] 



♦ KNOWLEDGE ♦ 



457 



about the sun, will be wholly useless, iiud can only be an 

 object of curiosity for the students of tlio Obscrvutory ; 

 but not to conceal any thins;, it is ]> issililo that only the 

 earth sends out from herself vajiours and exhalations gross 

 enough to produce twilights, and that Nature had reason 

 to provide, by one general means, for the necessities of all 

 the other planets, which are, if I may so say, of a purer 

 mold, and their evapoi-ations consequently more subtle. 

 "We are perhaps, among all the inhabitants of the worlds in 

 our vortex, the only persons who required to have a more 

 gross and thick air given us to breathe in. With what 

 contempt would the inhabitants of the other planets 

 consider us, if they knew this i " 



" They would be out in their reasoning," says the Mar- 

 chioness, " we are not to be despised for being enveloped 

 with a thick air, since the sun himself is so surrounded. 

 Pray tell me, is not this air produced by certain vapours, 

 which you have formerlv told me issued from the sun, and 

 does it m t serve to break the tirst force of his rays, which 

 had else probably been to excess? I conceive that the 

 sun may be veiled by Nature, to be more proportioned to 

 our use." 



"Well, madam," replied I, "this is some small introduc- 

 tion to a system which you have very happily started. We 

 may add that these vapours produce a kind of rain, which, 

 falling back upon the sun, may cool and refresh it, as we 

 sometimes throw water into a forge when the fire is too 

 fierce. There is not any thing liut what we may imagine 

 to assist Nature's address, but she has another kind of 

 address very particular, which is to conceal herself from us, 

 and we should not willingly be confident that we have 

 found out her method of eg ing on her designs in it. In 

 case of new discoveries, we should not be too importunate 

 in our reasonings, tho' we are always fond enough to do it ; 

 and your true philosophers are like elephants, who, as they 

 go, never put their second foot to the ground 'till their 

 first be well fixed." 



" The comparison seems the more rational to me," says 

 she, "as the merit of those two species of animals, elephants 

 and philosophers, does not at all consist in exterior attrac- 

 tions. I am willing to admit the judgment of both. Now 

 teach me some of the latter discoveries, and I promise you 

 not to make any rash systems." 



" I will tell you, madam," replied I, " all the news I 

 know from the firmament, and, I believe, the freshest 

 advices you can have. I am sorry they are not as sur- 

 prising and wonderful as some observations which I read 

 the other day in an abridgment of the " Chinese Annals." 

 Written in Latin. Those people see thousands of stars 

 at a time fall from the sky into the sea, with a 

 prodigious noise, or are dissolved, and melt into rains ; 

 and these are things which have been seen more 

 than once in China. I met with this observation at 

 two several times, pretty distant from each other, without 

 reckoning a certain star which goes eastward, and bursts 

 like a squib, always with a great noise. It is a great pity 

 that these kinds of phenomena should be reaerv'd for China 

 only, and that our part of the globe should never have 

 their share of these sights. It is not long since all our 

 philosophers were of opinion that they might affirm on good 

 grounds that the heavens and all the celestial bodies were 

 incorruptible, and therefore incapable of change ; and yet 

 at the same time, there were some men in the other part of 

 the earth who saw stars dissolve by thousands, which must 

 produce a very different opinion." 



" But," says the Marchioness, " did we ever hear it 

 allowed that the Chine.se were such great astronomers'! " 



" It is true, we did not," says I, " but the Chinese have 

 an advantage from being divided from us by such a pro- 



digious tract of earth, as the Crooks had over the Romans, 

 by being so much prior in time : distances of evcuy sort 

 pretend a right of im|Ki^ing on us. In reality, 1 think still 

 more and more, that there is a certain genius which has 

 never yet been out of the limits of Europe, or at least not 

 much beyond them ; perhaps ho may not be permitted to 

 spread over any great extent of the earth at once, and that 

 .some fatality prescribes him very narrow bound.s. Let us 

 indulge him whilst we have him ; the best of it is, he is not 

 link'd to the sciences and dry speculations, but launches out 

 with as much success into subjects of pleasure, in which 

 point I ((uestiou whether any people eiiual us. Those ar« 

 such topicks, madam, as ought to give you entertainment, 

 and compleat your whole system of philosophy. 



ENGINEERING CONSTRUCTION AT 

 THE INVKNTIONS EXHIBITION. 



ONE would almost think that engineering construction 

 would alone all'ord a sufficient display to constitute 

 an exhibition in itself. Indeed, although as a matter of 

 fact, one small section of the building has been devoted to 

 the hybrid Group III— engineering construction and archi- 

 tecture — the whole exhibition is, to a greater orle.ss extent, 

 stocked with products which would be equally in pUce were 

 they included in the third group. The group comprises 

 nearly liOO exhibits, some of which are large and highly 

 instructive. 



They are in the official catalogue prefaced by a concise 

 review, bristling with facts and figures, of the woik accom- 

 plished since the year 1SG2. Many of the features in this 

 preface have historical significance. Thus, we are told that 

 on May 2, 1862, two 21-feet steel rails were laid at the 

 Chalk Farm Bridge on the London and North-Western 

 Railway, for comparison with the ordinary rails, and were 

 taken up in August, 180") ; 'J,.">r)0,000 engines, trucks, ic, 

 weighing 'J5,.j0l),000 tons had i)assed over them. They 

 had" outlasted sixteen faces of the iron rails, while only 

 showing themselves a wear of about a quaiter of an inch. 

 Since that time the demand for steel rails has grown by 

 leaps and bounds, and to-day they are turned out at the rate 

 of 4,000,000 tons per annum. 



Considerable interest surrounds the details afforded con- 

 cerning the great European tunnels. The Mont Cenis 

 tunnel, 7' miles in length, traversing various strata of 

 rook, many of which were of the hardest character, was 

 commenced by hand labour in 18.58. In the first five years 

 the rate of progress by this means was 1 O.'i^ ft. per day at 

 the Modane end. The introduction by M. Hommeiller of 

 compressed air rock-drills driven by watei- power marked a 

 great advance, and the rate of progress increased to 3 -080 ft. 

 in 18G.3, and further to G G9.5ft per day in 1870, while at 

 the Bardonncche end the rates were 2118 ft by hand, 

 31! 1 ft by machine in 18(12, and 7'J8'.Jft in 1870. The 

 work was completed in 1871, having thus occupied fourteen 

 years. The St. Gotliard tunnel, 'J| miles in length, com- 

 menced in September, 1872, was comphted and opened for 

 traffic Jan. 1, 1882, having occupied nine years and two 

 months. The advanced heading was driven at the rate of 

 GG3 ft. per day at first, increased subsequently to 1011 ft 

 per day by the adoption of the Ferroux drill. The head- 

 ings, starting 9} miles apart, met with a deviation not 

 exceeding four inches vertically and eight inches horizon- 

 tally in less than seven and a-half years' work, the greater 

 progress being due to the improved rock-drills, the use of 

 dynamite, and compressed air locomotives. In the Arlberg 

 tunnel, Gy miles in length, which will form the connection. 



