206 GENEVA SOCIETY OF PHYSICS AND NATURAL HISTORY. 



ings taken by the engineer, M. Ph. Gosset, include the Swiss bank 

 of the lalje, from Saint Sulpice to Saint Saphorin, with the opposite 

 bank and the intermediary basin, which attains at this place its greatest 

 depth of 334: metres (1,000 feet) below the surface. The same number of 

 the ArcJiivcs contains a memoir of M. Ed. Pictet-Mallet, read before the 

 society during its session of January 7, 1875, and relating to an analo- 

 gous subject. M. Pictet-Mallet undertook the task of representing on 

 a chart, projected on a scale of ys^qo^ ^"^ traced with contour-curves 

 at equidistant levels of 5 metres, (LtJ feet) the configuration of the bottom 

 of the lower part of Lake Leman; that is, the space comprised between 

 Coppet, Hermance, and Geneva. The portion of this work nearest the 

 city is not yet completed, but it contains a thorough discussion of the 

 advantages and disadvantages of the different methods that may be 

 followed in the operation of soundings, and quite singular details about 

 the inequalities of bottom presented by the lake in the portion that has 

 been explored. 



M. Plantamour gave a summary of the observations relating to the 

 variations of the level of the lake during the year 1874. By the indica- 

 tions of the limnimeter of the Jardin Anglais (English Garden), the 

 mean annual level was within two millimetres, (one twelfth of an inch), 

 the same as that deduced from the thirty-six preceding years, but with 

 a greater annual variation than usual, say 1.G9 metres (67 inches), instead 

 of 1.44 metres (57 inches). From February to June, the level was below 

 the mean : the absolute minimum occurred on the 10th and 11th of March, 

 and was 9 centimetres (4 inches) below the mean annual minimum. 

 Per contra, from July to October, the level was above the mean, and 

 the absolute maximum exceeded by 16 centimetres (6 inches) the mean 

 level of high stages of water. The gauges established at two other 

 points of the canton of Geneva, at Secheron and Genthod, and at three 

 other points on the Vaudois shore, Ouchy, Vevey, and Chillon, the daily 

 readings of which were transmitted by the engineer of the canton of 

 Yaudois, (M. Gonin,) admitted of a comparison being made from day to 

 day, and from month to month, of the level of the lake on the right shore 

 along its entire length ; the zeros of all the scales of the gauges having 

 been made to correspond in the operations of running the level of Switz- 

 erland. By these observations it is ascertained that the inclination of 

 the lake is almost insensible from its upper extremity to IJ kilometres (1 

 mile) above the city of Geneva, the admitted level at Secheron being 

 duiiug the entire year within a few millimetres the same as at Vevey and 

 Chillon, and the chance depressions shown by the deviations among the 

 heights observed on the same day from one extremity to the other be- 

 ing very small and limited to a few centimetres. From Sdcheron to the 

 limnimeter of the Jardin Anglais, the slope is very appreciable, as might 

 hav^o been expected from the existence of a very sensible current in the 

 immediate vicinity of the city ; moreover, the inclination varies with the 

 season ; it is very slight in winter, and at the opening of spring, at the 



