NOVEMBKK 16, 18S3.] 



SCIENCE. 



657 



•cussion was continued In the next session with 

 remarks about the greater variability of the 

 ■error of colliination in the prismatic transit ; 

 but its superiority in its low Y's over the 

 ■common form of the instrument was recog- 

 nized. In connection with the pendulum of 

 reversion, Hirsch refers to the observations 

 ■of Mr. C. S. Peirce of the U. S. coast and geo- 

 detic survey, at Geneva, Berlin, and Ilobolceu 

 in America, which prove experimentally the 

 theoretical conclusion of the complete elimina- 

 tion of the resistance of the air by the use of 

 Bcssel's pendulum of reversion, — a conclu- 

 sion indorsed by Ferrero from experiments 

 made in Italy. In the fourth session, YiUar- 

 ■ceau explains the construction of his new appa- 

 ratus for the relative measure of the intensity 

 ■of gravity, and the commission recommends a 

 ■direct comparison of the new apparatus and of 

 the apparatus of Cellerier at a number of sta- 

 tions. A discussion followed on self-registering 

 tide-gauges and river-gauges ; Mr. Diesen stat- 

 ing, that in Holland as man^- as sixty-four in- 

 struments were in operation, or being put to 

 immediate use. Professor Nagel was elected 

 .a member of the permanent commission. In 

 the following session the business programme 

 for the seventh general conference of the 

 European association for the measurement of 

 arcs was formulated and adopted : viz., — 



1. Reading of the annual report of the per- 

 manent commission. 



2. Reports of the progress of geodesy by 

 the re|)resentatives of the several countries. 



3. Reviews of the present state of geodetic 

 ■operations, subdivided as follows : — 



Astronomical longitudes, latitudes, and azi- 

 muths (reporter, Baekhuyzen) ; Triangulations 

 (reporter, Ferrero) ; Base-lines and base-ap- 

 paratus (reporter, Perrier) ; Levels of precision 

 (reporter, Hirsch) ; Tide-gauges (reporter, 

 Ibauez) ; Gravity apparatus (reporter, von 

 Oppolzer) ; Refraction (reporter, von Bauern- 

 feind) ; Geodetic publications (reporter, Bae- 

 3'er) ; Arc of the parallel in Europe (reporter, 

 Faye). 



The proposition to meet at Rome in October 

 next is adojited, ponding the favorable accep- 

 tation by the Italian government. 



The remaining part of the pamphlet is occu- 

 pied with reports in detail of the progress made 

 during the years lH81-8'2 in the countries rep- 

 resented. Their contents maj' be briefl}- sum- 

 marized as follows : — 

 Baden. Germany. — Levels of precision, and 



jniblication of the results of the Rhenish tri- 



angulation. 

 Bavaria, Germanv- — Observations of terres- 



trial refraction, lateral and vertical; spirit- 

 levelling, total development to date 2,578 

 km. ; oscillations of the ground, and pendu- 

 lum observations at the Bogenhausen obser- 

 vatory. 



Denmark. — The fourth volume of the geodetic 

 survc}- is promised towards the close of 1883. 



France. — Connection b}- new triangulalion of 

 the base-lines of Melun and of Perpignan ; 

 extension of the Algerian arc of the parallel 

 into Tunis ; measures of latitudes and of 

 differences of longitude by telegraph. Vol- 

 ume xii. of the ' Memorial du depot de la 

 guerre ' is in press, and a table of logarithms 

 of eight places of decimals is in preparation. 



Hesse, Germany. — Levels of precision, mean 

 error per km. equals 2.27 mm., from 152 dif- 

 ferences in levels, connected by 14 condi- 

 tional equations. 



Holland. — Connection of lines of spirit-level- 

 lings with lines of adjacent countries ; total 

 length levelled, 283 kin. 



Ital3-. — The reconnaissance for the primary 

 and secondar3' triangulation completed ; geo- 

 detic levelling and tidal observations ; deter- 

 mination of a latitude, an azimuth, and of 

 several differences of longitude, by telegraph ; 

 comparative pendulum observations at Rome. 



Austria. — Measure of astronomical latitudes ; 

 telegraphic determinations of dilierences of 

 longitude ; pendulum cxperimouls ; triangu- 

 lations and astronomical work in general ; 

 occupation of points, and attempts of meas- 

 ures of angles, in the high Alps (among 

 these Ankogl at an elevation of 3,2t)3 m. ; 

 station Grossvenediger, of 3,05;) m. : and 

 of Grossglockner, of 3,798 ra.); extension of 

 triangulations in Bosnia, Herzegovina, and 

 Dalmatia : continuation of levelling opera- 

 tions in Austria proper, and in Hungary ; 

 observations of the intensity of gravity in 

 the deep mine of Pril)ram. The work exe- 

 cuted in this country' is too extended and 

 diversified to be given here in detail : it is 

 graphicall}- represented in a finely executed 

 map in color-print. 



Portugal. — Continuation of the triangulation 

 and of tid.il observations. 



Prussia. — Revision and completion of princi- 

 pal lines of levels. The following im))ortaut 

 results are recapitulated : Atlantic higher 

 than the Mediterranean from levels between 

 Swineraundc on the Baltic, and 3Iarseilles, 

 vid Switzerland, O.GG4m. ; Swinemunde to 

 the Mediterranean, vid Amsterdam and Os- 

 tend, O.G58m. ; and Santander to Alicante, 

 in Spain, 0.(>G2 m. The discussion of the 

 tidal observations at Swinemunde showed no 



