360 



• KNOWLEDGE • 



[Oct. 



sarfaces air l>oth convex. The flint glass lens (concave on 

 l>oth sides) has for the surface next the crown lens a radius 

 of 73 4 inches. That of the surface next the eje is 222 -2 

 inches. The distance l>et ween the lenses is 7 -r) inches. The 

 focal length is .10 feet 1 inch. The steel tube of the tele- 

 scope has a length of 2S feet and a d:anieter cf 33 inches 

 in the middle. The length of the polar axis is 10 feet; 

 diameter at bearings, 8 inches and 6 inches. The diameter 

 of the coarse hour circle is 30 inches ; of the fine hour 

 circle, 28 inches. The length of the declination axis is 

 9 feet; its diameter at bearings, 7i and fti inches. The 

 diameter of the declination circle is' 30 inches. 



The driving weight of the clockwork weighs 320 pounds, 

 and has a fall of 12 feet The radius of the sector l)y 

 which the clockwork drives the telescope is 40 inches. The 

 centrifugal regulator or governor weighs 22 pounds, and 

 revolvi's once in seven-tenths of a second. Tlie weight is 

 taken off the lower pivot by floating the regulator in 

 nuroury. The weiglit of the telescope and mounting is 

 aUut seven tons. The height of the centre of motion 

 above the floor is 20 feet 9 inches. The declination circle 

 is read from the eye end of the telescope by microscopes 

 9 feet long. 



Tlie telescope is provided with position and double-image 

 micrometers of the best construction. The star spectroscope, 

 by Hilger, of London, was constructed under the super- 

 vision of Mr. Christie, the Astronomer Royal, upon the 

 same plan as that of the instrument for some time in use 

 at Greenwich, but upon an enlarged scale. It is a direct- 

 vision instrument, with three (.so-called) half prisms. It is 

 more than 6 feet long, and weighs, with its appendages, 

 about 1 rtO pounds. For the present it is expected this 

 telescope will be devoted mainly, though not exclusively, to 

 stellar spectroscopy. 



For the purpose of comparison the following facts with 

 regard to other large refracting telescopes will be found of 

 interest But two instruments excelling the Princeton 

 telescope are now in use, namely, the 25-inch telescope 

 made by Cooke, of England, and owned by Mr. Newall, 

 of Xewcastle-on-Tyne ; and the 2G-inch equatorial, made 

 J)y the Clarks, at the Naval Observatorj-, Washington. 

 The third larger instrument, made by Grubb, of Dublin, 

 and having an aperture of 27 inches, is now in process of 

 tDOunting at Vienna. 



The instrument nearest in size below the Princeton tele- 

 scope, now in use, is the Strassburg refractor, with an 

 aperture of 1 9 inches. There are in process of construc- 

 tion five larger instruments, namely : — 



The Poulkowa telescope, 30 inches, and the McCormick 

 telescope, 26} inches; both by the Clarks. The Henry 

 Brothers, in Paris, are making a 29-inch telescope for the 

 Nice Observatory, and another, of the same size, for the 

 National Obser\-atory at Paris. One of the disks of glass 

 (the crown) for the Lick telescope, to be 36 inches in 

 diameter, hag been received by the Clarks, who are waiting 

 for the flint disk before beginning the grinding. This 

 ^gantic instrument, when tini.shed, is to be erected on 

 Mount Hamilton, California. — SrUnliJir Americnn. 



Cost of One Home- Power. An American contempo- 

 rary says : — According to the following excerpt from the 

 SrJiool of Mirifs Qu/irl'.rhj, the cost of one horse-power per 

 hour is a8 follows, from experimenti lately made at 

 CarLsruhe : 100 h.-p. steam engine, -'3') pence ; 2 h.-p. 

 steam engine, ."JoO pi-nce ; 2 h.-p. I>-hraan'8 caloric engine, 

 3-31 pence ; 2 h.-p. Hock motor, 1 00 pence; 2 h.-p. Otto 

 ga*-en;,ane, 3 26 pence; 2 h-p. Otto-Langen gas-engine, 

 3-^6 pf-nce ; 2 h.-p. Schmidt water-engine (fed by city 

 water fcupply), 11-87 pence: horses, 2.') 00 pence; men, — . 



J\rbirU)£{. 



BACKBONED ANIMALS.* 



IT were enough to say of this book that it is a work by 

 Miss Buckley to commend it at once to our readers, 

 for of Miss Buckley, as of Mr. Cr.ant Allen and one or two 

 others (would there were more), it may truly be said 

 that they have published nothing \\'hich has not been 

 charming. 



Miss Buckley speaks as if she could not keep silent, so 

 much her subject interests her, yet all the time she speaks 

 as if she had her audience always before her, and felt she 

 must make clear to all what is so clear and simple, and 

 withal so charming, to herself. She does not seem, like so 

 many writers about science, to think that she will gain no 

 credit for profundity if she does not use words a-foot-and 

 a-half long. So far from that she invents simple words to 

 replace the Greek and Latin terms with which foolish folk 

 in past times chose to clothe and cloak their ideas. She 

 does not speak, where she can help it, of Yi'rtehratf. but of 

 Jiarkhoned animals, not of ifamnmlian^ but of Milk-givers., 

 not of Marsupitih but of I'onchid animals. She writes, in 

 fact, as if she wanted to be understood and wanted to 

 interest her readers in her subject, whereas some of our 

 naturalists have written as if that were the last thing in 

 the world which a science-writer should aim at, the main 

 motive for writing being (they seem to assume) to show 

 how learned and profound the writer is. 



But Miss Buckley's book is very difficult to review. Not 

 a page in it fails to attract and to suggest reflections. 

 There is not a chapter from which one wou'd not like to 

 extract at least half. 



Not being able to do this, we note that Miss Buckley 

 takes the several members of the backboned family, and 

 shows how each of them is related to ancestral forms, 

 " restorations" of which appear in the picture headings of 

 the several chapters. It must be admitted, by the 

 way, tiiat these picture-headings suggest ideas somewhat 

 like those which boys must form from the study of 

 Mr. Ballantinc's books — "The Fir Trader," "The 

 Coral Island," "Gorilla Hunters," rt hoc r/nivs ounv'.. 

 One would suppose life with these primaeval crea- 

 tures must have been a scene of perpetual adven- 

 ture. Thus we have in a space less than a quarter of 

 a mile square, a Deinolherium and a Mastoilon, three HeUa- 

 dolherifi, or ancient giraffes, a Jlippopotamus, a Tnpir, a 

 Rhinocfrns, a Hydra, an Antrhipr, and a small monkey, 

 I'ithrcus I't'nldicuH. On the cover, a Zebra is added, and 

 for the Deinotherium, towards which, at p. 2.')6, a Hippo- 

 potamus is advancing with an expression showing that he 

 is not quite sure whether tho.so inverted tusks will quite 

 suit him, a nondescript horned animal (presumably an 

 ant<!lope, but the horns arc not right) is substitutc^d, which 

 seems likely to fare ill between the Hippopotamus and an 

 Elephant (Mastodon) and Rhinoceros, who are eyeing it 

 more intently than encouragingly. Of course, the primieval 

 woods, and streams, and lakes were never so closely 

 crowded with inhabitants as they are shown in such 

 pictures ; but, for purposes of illustration, these pictures 

 do very well. In fact, there is no other way of treating 

 such subjects without greatly multiplying the number of 

 pictures. 



The illustration's, by Mr. Carreras, jun., Mr. Coombe, 



• Wirmtrx in Life's Race, or the Great Backhoned Family. By 

 AiunKi.LA IJ. KucKl.KY, author of "The Fuiry Land of .Snience," 

 "Life and licr Children," Ac. (Edward Stanford, London.) 



I 



