October 25, 1900J 



NATURE 



623 



and the desirability of continuing measurements outside 

 middle latitudes to which they have hitherto been almost 

 ■entirely confined, a project involving so many hardships 

 might well be abandoned. Not the least interestmg part 

 of the report of Captain Maurain is his description of the 

 country in which the pioneers of the last century carried 

 out their observations, often on the slopes of mountains 

 rising abruptly to the height of some 3000 metres. Of this 

 monumental work scarcely a vestige remains, and the 

 original line of route can be traced only from the written 

 records. The care with which the fundamental points in 

 a triangulation are now marked was not appreciated in 

 those early days, and even the pyramids constructed to 

 commemorate the ends of the arc, and the successful 



Fig. I.- '1 he sh.ided poition of the- map shows the district in which the 

 ineasuremenis will be made. 



termination of the work, have been demolished by the 

 Indians, who hoped to find buiied treasure under the 

 monuments, though the jealousy of the Spaniards has led 

 to almost equally deplorable results. 



But the enterprise of tlie French will not be contented 

 with the simple re-nieasurenient of the arc of Bouguer, 

 which extended from the environs of Quito on the north 

 to Cuenca, somewhat south of Guayaquil (F'ig. i). 

 Captain Maurain's instructions led him to examine the 

 -country north and south of these stations, with the view 

 •of e.Ktending the arc to six degrees of latitude. In 



NO. 1617, VOL. 62] 



neither direction does the task become more simple. 

 Towards the north the two chains of the Cordilleras 

 unite in a confused mass, bristling with numerous 

 summits, rising to an altitude only less than that of 

 Chimborazo or Cotopaxi. On the southern side the 

 country becomes more open, but covered with forests, 

 and with a wet climate, suggestive of fever. Neverthe- 

 less, it seems possible to push northwards as far as Paste 

 in Columbia, and southwards to the Peruvian town of 

 Sullana, an arc of six degrees, or about double that 

 originally measured. The Finance Minister asks, as 

 Finance Ministers will, whether it is absolutely necessary 

 to carry the arc beyond the limits of the ancient survey, 

 and the answer of the French Academicians, as might 

 have been anticipated, is to insist on the inaintenance of 

 the whole scheme as contemplated in the preliminary 

 examination. 



The entire programme is vast, and worthy the best 

 traditions of French science. Three bases of about 

 eight or nine kilometres in length will be measured, one 

 approximately central, and two of verification at the north 

 and south ends respectively. The difference of level 

 between the central base and the sea at Guayaquil, 

 where tide gauges will be erected, will be determined 

 with the greatest nicety. Throughout the arc fifty-two 

 stations will be selected for observation, of which three 

 will be fundamental, and the longitudes be determined by 

 telegraph. Magnetic observations will be carried on as 

 a matter of course, and in a country marked by so many 

 mountain masses special care will be taken to deter- 

 mine their extent and density, with the view of eliminating 

 the effect of local attraction. But, after all precautions, it is 

 not impossible that the measures be made on a lengthened 

 protuberance on the surface of the geoid, and that the 

 curvature of the line of route should differ sensibly from 

 that which would be found along a line nearer to the 

 Pacific or further inland. To decide this point, two 

 methods are proposed — one by means of pendulum obser- 

 vations, which will give the variation of gravity throughout 

 the whole region ; the other, by determining the difference 

 of geodetic and astronomical longitudes between a point 

 on the coast and the observatory at Quito. The army 

 of experts who have examined the plan and arranged 

 the details assures us that no difficulty has been over- 

 looked, and as a result an admirably equipped expedi- 

 tion will leave France next spring, to take up quarters 

 on the equator, where four years' hard and anxious work 

 awaits the members. 



As already mentioned, towards the polar end of the 

 quadrant the expedition under the Russians and Swedes 

 has already made good progress. The arc measured 

 by Maupertuis and Clariaut extended through only fifty- 

 seven minutes in the latitude 66^, and Svanberg at- 

 tempted no greater distance than iV. But the modern 

 scheme includes an arc of more than 4^ in length, in the 

 much higher latitude of 77'-8i°. The general control 

 is in the hands of H. Sergieffsky, and trained as he has 

 been in the accurate school of Pulkowa, admirable re- 

 sults may be expected. The difficulties to be encountered 

 are probably not less, though of a different kind to those 

 that await the French in the tropics. Fifty stations will 

 be occupied in the course of the triangulation, which 

 compares satisfactorily with the fifty-two of the French 

 scheme. Two baselines only will be measured, in which 

 it is proposed to use Jaderin's steel tape line twenty 

 metres long. Very little is known of the success that 

 has attended this method, though its accuracy is vouched 

 for by Dr. Dollen's careful examination, and the French 

 prefer to rely upon the same apparatus that was used in 

 the determination of the French meridian. It was ex- 

 pected that the field-work in Spitsbergen would be 

 finished this summer, but we are still waiting information 

 concerning the amount of progress that has been made. 



Lacaille's arc of meridian, measured in 1752, and 



