174 



NA TURE 



[June 21, 1894 



nouce on iiiv part uecause i; ioipujns not only the verbal 

 sta'-ements made to many as'rononiers who have inspecled 

 the instruments of the L.S Nival Observatory, but alio the 

 correctness of an official report mide by m; to the Sopetin- 

 tendent of the Naval Observatory, and appended by him to his 

 report for the year 1S93, printed c ipies of which have been dis- 

 tributed to nearly all the observatories in the world. 



The paragraph in qutstion is based upon an illustrated article 

 in the Z; ./. . ■ .'/ ///r Initrununteiihum:!-, 1894, 14 Jahrgang. 

 pp. 12S-130, which purports to be a description of the I2inch 

 e'laatorial telescope of the Georgetown College Observatory, 

 and in nhich it is asserted (l) that the instrument was con- 

 structed nearly thr-e years ago by Mr. Geo. N. Saegmuller, of 

 Washington, D.C. ; (2) that its principal novelty i-i a pair of 

 star dials, or finding circles; and (3) that similar instruments 

 have been constructed by Mr. Saegmuller for the U.S. Naval 

 O'jservator}' at Washington, and for other institutions which are 

 nameH. From these statements the writer of the " .\stronomical 

 Column'" very nalurallv inferred that Mr. Saegmuller con- 

 structed these dials, or finding circles, three years ago, when in 

 reality be did nothing of the kind. The facts are as follows ; — 

 The idea of these finding circles first occurred to me while the 

 question of building a 12-inch equatori.al mounting for the L.S. 

 Naval Observatory was under consideration, and in the specifi 

 cations for that iasirtiment, which were dated .May 20. 1S91, I 

 embodied it in these words : " Connected with them (the quick 

 motions) and arranged so as always to face a person operating 

 them, suitable indicators shall be provi led for showing auto- 

 matically the right ascension and declination of the point to 

 which the telescope is directed." Mr. Saegmuller got the con- 

 tract for building that mounting, and the details of these indi- 

 cators were arranged between us. The erection of the mouniini; 

 at the Naval Observatory was completed in November 1S92, 

 and almost immediately thereafter NIr. Saegmuller put an exact 

 copy of its indicators upon the Georgetown College telescope, 

 whuli lie hotl trecleii some time picioiisly. Finally, the two 

 woodcuts which illustrate the Zd'.s.'irijTs article are not pic 

 tures of the Georgetown College telescope, but of the Naval 

 Observatory telescope, which differs from the Georgetown 

 instrument in many details. Wm. H.krkness. 



Washington, D.C, June 7. 



On the Use of Quartz Fibres in Telescopes. 



Peru vrs it miy interest some of your readers to know that 

 the qaarii fibres of Prof. Boys afl'ords an excellent material 

 for providing the eye-lens of telescopes, and specially the 

 ins'niments used in combination with rcflorling galvanometers 

 and electrometer-;, with threads required for their adjustment on 

 the divisifjns of the scale. I thought at first that as the fibres 

 ap[>t;ar, when examined with the microscope, to l)e semi.tr.-ins- 

 parent and have a silver-grey colour, they would, when seen 

 l)ehin<i the ocular len«, not present Ihemselv.s as distinct and clear 

 lines, but as aniaHerof f.-ict, when they were put at the proper dis- 

 tance, they showed an intense bla<k colour, even darker than the 

 divisions made with ink on the scale on which the instruments 

 were focu^«ed. I used threads of 20 microns diameters, and 

 ihey can be fixed on the diaphragm without much difficulty by 

 means of a mixture of resin and mastic applied with a he.ated 

 wire, and this mixture answers better than brittle shellac. It is 

 obviouj that the ihreails, »hen Uid down in the diaphragm, are 

 at once stretched, and remain in g jod condition, as they are 

 not affected in any appreciable degree by the influence of heat 

 and atmospheric moiciare. L. Bleekroi'K. 



The Hague, June 18. 



Bullet-Proof Shields. 



Is reply to a letter 0.-1 bullet-proof shield', in the last number 

 of N'A'IlJRe, I wish 10 Mate that some preliminary expetimenlk 

 with sphere* show that the cnerjfy of the shot is traDsmilled 10 



direction of the blow, to -uch 

 : to the board to which the 



.,..••- — ; the case when rods are used. 



1 hope thoitly to give the details of my experiments on the 

 fot'JcC. FkKtiERlCK J. S.Mirii. 



OACord, Jane 16. 



THE HORX EXPEDITION FOR THE SCIEX- 

 TIFIC EXPLORATIOX OF CEXTRAL 

 AiSTRAUA. 



TNFORM.-\TION has been received of the organization 

 •'• and despatch from .■\delaide of a new and well- 

 equipped eNpedition for the scientilic exploration of the 

 Macdonnell Ranges which lie about eleven hundred 

 miles to the northward of that capital and nearly in the 

 centre of the Australian continent. The expense of this 

 expedition is borne by a wealthy and public-spirited 

 colonist of Sotith .-\ustralia, Mr. William .-Austin Horn, 

 who thirty years ago carried out on his own account 

 some explorations in the Gawler Ranees, and has since 

 taken a very active part in the development of the mineral 

 resources of the country, besides being a prominent 

 member of the colonial legislature and of the Council ol 

 the University of Adelaide. Mr. Horn himself is the 

 leader of the present Expedition, but has wisely associated 

 with him some scientific gentlemen of great experience 

 in .-Australian travel. .-Vraong them are Mr. Charles 

 Winnecke, of the Trigonometrical Survey of South 

 .\ustralia, who in the performance of his duties has re- 

 peatedly traversed some of the most arid country of 

 the continent, and has mapped out souie thirty thousand 

 square miles of its surface. With him also goes as 

 medical officer. Dr. E. C. Stirling, C..M.G , F.R..S., of the 

 University of .Adelaide, the well-known discoverer, a few 

 years since, of Xoioryc/es, and latterly the investigator 

 of the D/pro/oifo/i-deposas, the results of which so 

 many are impatiently expecting, though now it is clear , 

 that for them they will have to await his return from 

 this new undertaking, the charms of which he found it 

 impossible to resist. Besides these there are of the 

 party, Prof. Ralph Tate, also of the University of .Ade- 

 laide, and President of the last meeting of the .Austra- 

 lasian .Association for the .Advancement of Science, 

 eminent as a pala;ontologist, and especially as a paUeo- 

 botanist, as well as Prof. Baldwin Spencer, whose name, 

 from his connection with Owens College and Oxford, 

 will be at once recognised by all ; while there is also Mr. 

 J. Alexander Watt, of the Geological Survey of New- 

 South Wales, to pay special attention to mineralogy and 

 petrology. In the capacity of collecting naturalists, Mr. 

 K. W. Belt, of Adelaide, and Mr. G. A. Keartlanil, of 

 Melbourne, complete the start" of the expedition, which 

 will be accompanied by thiee camel-drivers, a couk, and 

 two prospectors sent by the Government. The Expe- 

 dition was to leave Adelaide on May 3rd for Oodnadatta, 

 and thence proceed along the telegraph line as far as 

 Lilia Cieck, where it will turn to the westward towards 

 the Avers Range and Goyders Springs, after which it 

 will make for the Palmer River, and then, deviating again 

 to the westward towards Petermann Creek, will return to 

 the upper valley of the Kinke River, and then push on 

 to Glen Helen at the foot of the Macdonnell Ranges. It 

 will of course be understood that circumstances may 

 cause this plan to be modified more or less extensively; 

 but from the previous experience of those who have laid 

 down the route to be taken it will probably be carried 

 out pretty much as is intended, though some of the 

 country to be traversed is absolu'.cly unexplored, and 

 much of it very imperfectly known. Wherever a prospect 

 of doing woik'is found, a longer or shorter halt will be 

 made, and as the Expedition is to be well furnished with 

 camels— no fewer than twenty-three being taken with 

 it— the dilticulties that attend the needful supply of water 

 will be reduced to a minimum, while it is said that 

 owing to recent good rains in the latitudes to be passed 

 through everjlhing looks promising for a successful 

 journey. 



The imporlarce of this undertaking is not easily to be 

 over-tated. Expeditions of one kind or another to the 

 interior of the continent have been numerous, and 



NO. I2S6, VOL. 50] 



