846 



SCIENCE. 



[N. S. Vol. VIII. No. 207. 



who had never been known to use anything 

 but his native tongue at the meetings, re- 

 sponded ' Ja.' 



Before closing the present paper, atten- 

 tion should be called to a few points of in- 

 terest noted during the trip to Stuttgart 

 and return. A. flying visit was made to the 

 Eoyal Observatory at Berlin, the Eeichsan- 

 stalt at Charlottenburg, and the Geodetic 

 Institute at Potsdam. At Paris the ofiaces 

 of the geographic service and the Interna- 

 tional Bureau of Weights and Measures 

 were examined, and part of one day was 

 devoted to the English Ordnance Survey 

 at Southampton. 



An interesting object at the Berlin observ- 

 atory is the instrument with which Kiist- 

 ner discovered the variation of latitude. 

 Not alone because of the splendid result 

 achieved, but on account of the conditions 

 under which the work was done. It is 

 mounted on a pier more than twenty feet 

 above ground, on a subsoil of sand, in the 

 middle of a city, with bad atmospheric 

 conditions and about one hundred feet from 

 the public thoroughfai'es. In spite of these 

 adverse circumstances a new fact was 

 added to science, which had baifled the 

 efforts of larger telescopes under immeasur- 

 ably better conditions. There is much en- 

 couragement in this to investigators with 

 scanty means at their disposal. 



At the Aichungs-Kommission a balance 

 was shown which easily determines the 

 weight of a kilogram with an error of 1/200 

 ■of a milligram, being 1/200,000,000 part of 

 •the quantity sought. They have also a 

 ■complete series of weights in quartz from 1/2 

 ;gram to one kilogram, and thermometers 

 giving the temperature by estimation to 

 I/IOOO of a degree Centigrade. 



At Charlottenburg the most striking fea- 

 ture was the extension and perfection of 

 the organization. Nine buildings in all, of 

 which the two larger are devoted, one to 

 theory and the other to practice, have cost, 



together with the running expenses since 

 1887, 3,000,000 Marks. The annual outlay 

 is at present about $90,000. 



The Geodetic Institute at Potsdam has 

 been much less expensive, and presents 

 many admirable points of arrangement 

 and administration. Among the details 

 may be cited : the clock room, always 

 maintained at a temperature between 20° 

 and 21° Centigrade; the pendulum room, 

 artifically heated on all sides, including the 

 floor ; a pillar over fifty feet high, and cor- 

 respondingly thick, with meridian marks 

 several miles away, to study changes in 

 azimuth and the movement of the earth's 

 crust ; and finally a small photographic in- 

 strument, by means of which the occupa- 

 tion of a station only requires S minutes, 

 and gives a determination of the geogra- 

 phical position in latitude within two sec- 

 onds of arc. The subsoil, as at Berlin, is 

 nothing but sand. 



At Sevres, near Paris, several interesting 

 instruments were seen, among which may 

 be especially mentioned that designed for 

 the comparison of the metre with the wave- 

 length of light following Michelson's method, 

 and the apparatus for the determination of 

 coefBcients of expansion according to the 

 method of Fizeau. Some recent experi- 

 ments have been made on a composition 

 containing 36% nickel and 64% steel. It 

 appears that the expansion from heat is 

 thus reduced to about 1/50 of what we 

 should expect from the individual com- 

 ponents. This discovery will simplify enor- 

 mously the solution of problems where the 

 temperature question has thus far been the 

 great diflBculty. It will, for example, be a 

 comparatively easy matter to make pendu- 

 lum clocks run with a daily correction of 

 about 1/10 of a second per day under vary- 

 ing temperature conditions. 



At the oflBce of the geographic service of 

 the army a noteworthy feature was the 

 publication of charts. Six presses, each 



