244 ADDITIONAL NOTICES. [June 25, 1860. 



the standards employed. This last measurement, effected by means of tubular 

 iron rods, which had been submitted to the closest examination and experi=» 

 ments with regard to their dilatation under various temperatures, gave a result 

 of 13,053-74 metres or 40,185-208 French feet. The base measured by M. 

 Feer in the Sihlfeld, near Ziirich, having been reached by 14 triangles based 

 on the new measure of the base at Aarberg, was calculated to be 3,360*256 

 metres, while an actual new measure gave 3,359*930. The connection of the 

 triangulation with those of other countries offers a convincing proof of the 

 accuracy of the Swiss measurements. The length of the side Roemel to Faux 

 d'Enson was calculated by the French engineers as 35,997-22 metres, while the 

 Swiss triangulation makes it 35,997-27 metres. The side Pizzo Forno to 

 Pizzo Menone di Gino was found by the Austrian Staff to be 44,572-77 metres, 

 and by the Swiss 44,572-12. 



The number of primordial triangles is 110; 14 of the stations are more 

 than 3000 metres above the level of the sea, 22 from 2500 to 3000, and 15 

 from 2000 to 2500 metres. The number of triangles of secondary order 

 was 443 in 1840, but has been greatly increased since. With some of 

 them it has been found impossible to observe the three angles owing to 

 the inaccessible nature of one of them, and the consequent impossibility of 

 establishing signals and stations on those points. Most of the highest summits 

 in Switzerland are included in this class, thus giving a peculiar interest to the 

 hypsometrical results of the secondary triangles. 



The latitude of the Observatory at Berne, as determined in 1812 by MM. 

 Henry and Delcross, of the French Geographical Engineers, and by Prof. 

 Trechsel, by 382 observations of zenith distances of the Polar Star, was 

 46^^ 57' 8"63", but by a trigonometrical connection of Berne with Paris made 

 by the French Engineers it was fixed at 46° 57' 6-02". The last has been 

 adopted by MM. Dufour and Eschmann on account of its coincidence with 

 the position arrived at from their comparison of the latitudes of Zurich and 

 Geneva, as determined by MM. Eschmann and Alfred Gautier. For the same 

 reason the longitude of 'Berne has been adopted as it was determined by the 

 French triangulations, viz., 5^ 6' 10-8" E. of Paris. 



The heights above the level of the sea have been determined by a compa- 

 rison of the Mt. Chasseral in the Jura, as given by the French measurement, 

 and its altitude above the level of the base at Aarberg. Care has been taken 

 not to attempt the measurement of inaccessible points except by comparison 

 with other points placed in about the same circumstances. Angles and obser- 

 vations taken from points much inferior in height and placed at a short 

 distance are of less value than those taken from more distant stations, as the 

 summits being generally rounded at the top are more in evidence at the 

 greater distance. Snowy crests are, besides, subjected to variations in height 

 of perhaps seven metres, owing to the melting or evaporation of the snow. It 

 will never be possible to determine exactly the height of Mont Blanc. 

 According to the measurements of the Sardinian engineers from Mont Colombier, 

 with the factor 0-078 for refraction, its altitude is 4799*70 metres, and from 

 Mont Granier, with the factor 0-076, it is 4,804-03 : by M. Puissant in the 

 * Nouvelle Description Geometrique de la France,' it is stated to be 4808*32. 

 The Swiss measurements have given the following results : from the Moleson, 

 with the factor 0*080, it is 4,801*9 ; from the Signal de Bougy, with the factor 

 0*075, it is 4,803*0 ; and from the same station, with the factor 0*080, it is 

 4797*8 metres. The very great attention paid to these observations may 

 lead to a better knowledge of the laws of refraction and a better determina- 

 tion of the heights of mountains. 



General Dufour has adopted a mixed method of representing the ground, 

 viz., the vertical light with moderate proportions of shading for the relatively 

 flat and undulating tracts, and the old system of oblique light under an angle 



