104 REroBT— 1882. 



'En resume le maximum d'ecart da sud au nord entre le fil et son 

 image a ete egal a 49"'2 (this is 15"'94; it seems as though this should 

 be twice the deviation of the vertical) le 30 Novembre a 8h. 43m. du 

 matin. Ce meme jour, a 7h. 28m., on a la 40""1, chiffre porte ici au 

 tableau, et 87'^'6 seulement a Ih. 82m. da soir. Dans I'espace de six 

 heures la verticale a done varie de 2"'5 ou 0"'81 (as this is the deviation 

 of the image, should not the deviation of the vertical be half as much ?). 

 Le minimum de I'annee, ou 3'06, fut atteint le 19 Janvier a 3h. 3m. du 

 matin, ainsi que le 21 du meme mois a midi, bien qu'on eut observe 3"44 et 

 3'30 dans les matinees de ces deux jours, ainsi qu'on le voit au tableau 

 ci-apres .... Pendant I'annee entiere la verticale, consideree selon le 

 plan du meridien, a done varie d'un angle de 12"-45 ou4""034 .... On 

 aura .... 8"'3 ou 2"' 7 pour la plus grande variation dans le sens Est- 

 Ouest ou Ton nivelle les tourillons des lunettes meridiennes.' 



Towards the end M. d'Abbadie makes the excellent remark, that in 

 discussing latitudes and declinations of stars, account should be taken of 

 the instantaneous position of the vertical at the moment of taking the 

 observation. 



In the 'Archives des Sciences,' 1881, vol. 5, p. 97, M. P. Planta- 

 mour continues the account of his observations on oscillations of the soil 

 at Secheron, near Geneva. The account of the earlier observations, 

 which we quoted from the ' Comptes Rendus ' in our previous Report, are 

 also contained in vol. 2 of the 'Archives,' p. 641. The paper to which 

 we are now referring contains a graphical reproduction of the previous 

 series of observations, as far as concerns the daily means. 



The new series extends from October 1, 1879, to December 31, 1880, 

 the disposition of the levels being the same as was described in our last 

 Report. The observations were taken at 9 a.m. and G p.m., which hours 

 are respectively a little before the diurnal minimum and maximum. The 

 meaning of the terms maximum and minimum were somewhat obscure in 

 the ' Comptes Rendus,' but I now find that the right interpretation was 

 placed on M. Plantamour's words, for maximum means for the two 

 levels E. end highest and S. end highest. 



The N.S. level seems to have behaved very similarly in the two years 

 of observation ; the total annual amplitudes in the two years being 4"'89 

 and 4"-56 respectively. In both years this level followed, with some 

 retardation, the curve of external temperature, except between April and 

 October, when the curves appear to be inverted. The E.W. level be- 

 haved very differently in the two years. In 1879 the E. end began to 

 fall rapidly at the end of November, and continued to fall until De- 

 cember 26, when the reading was — 88'''71 ; it rose a little early in 

 January and then fell again, so that on January 28, 1880, the reading 

 was - 89"'95. The amplitude of the total fall (viz. from October 4, 1879, 

 to January 28, 1880) was 95"'80. In the preceding year the amplitude 

 was only 28"'08. The E. end has never recovered its primitive position, 

 and remains nearly 80'' below its point of departure. 



It is difficult to believe that so enormous a variation of level is 

 normal, and one is tempted to suspect that there is some systematic error 

 in his mode of observation. If such oscillations as these were to take 

 place in an astronomical observatory, accurate astronomical observations 

 would be almost impossible. 



I have seen nothing which shows that M. Plantamour takes any 

 special precaution with regard to the weight of the observer's body, nor 



