130 Geographical Collections. 
bour, and thus the expedition has procured for us measures of the variation, of the 
inclination, and of the magnetic intensity for Toulon, the Isle of Bourbon, Pon- 
dicherry, Calcutta, Chandernagor, Rangoon, Daoubiou, Karical, Trincomalee, 
Jaffnapatnam, Aripo, Changani, Batavia, and Simon’s Town. 
All the observations have been made with the greatest care. The results of 
the different needles have every where agreed, as much as an experimenter in a 
sedentary observatory might have desired. The observations on the horizontal 
needle, will fix several points of the line of no variation. The observations on 
the inclination will be no less useful ; for they will serve to trace the magnetic 
equator, whose position in India is only founded on ancient and rather imperfect 
admeasurements. 
The discussion of these precious observations, will no doubt confirm what has 
already been discovered upon the motion which gradually transports the line of 
no inclination from east to west; and they may also assist in deciding a yet un- 
certain question, viz, whether the motion of this curve is or is not accompanied 
by any change in its form. 
The attentive examination which we have made of the observations of intensi- 
ty, has shown us that their discussion will be accompanied with some difficulty : 
the needles have in fact lost, during the voyage, a notable part of the magnetism 
with which they were endowed at the moment of departure; but the attention 
which was given to observations made at Pondicherry, in several places where 
they stopped, and the observations of Paris in 1827, compared with those of the 
commencement of 1829, will permit us, we have every hope, to determine the 
amount of that loss, and to obtain comparative results. 
Your commissioners do not think that they should pass over to another part of 
the report, without bringing into notice the names of the observers who studied 
magnetical phenomena. We shall in consequence mention, that the observations 
of Paris of 1827 and 1829, are those of Mr. de Blosseville. The observations 
made at Toulon, previous to the departure of the expedition, belong to the com- 
mander and to the young lieutenant whom we have just named. The measures 
made of this inclination at Pondicherry, at the first stay, and of the variation, 
inclination, and intensity at Rangoon, are by Messrs. Fabré and Janneret. Every 
where else, the researches on terrestrial magnetism, have been exclusively en- 
trusted to Mr. de Blosseville. = 
In this occupation, extremely fatiguing and delicate, this officer had been often 
seconded by a young seaman, Mr. Bassé, who perished at Batavia, the victim of 
his zeal. . 
The meteorological observations made on board the Chevrette, during the dif- 
ferent navigations, will constitute one of the most interesting acquisitions which 
natural philosophy has for some time reeeived. These observations are detailed 
with the greatest order in four registers: the instruments employed had been 
compared with the most exact that could be obtained, previous to the departure 
of the expedition, and have been verified on its return. The errors which might 
have arisen from the radiation of the vessel, have been avoided as much as pos- 
sible. In fact, this part of the labour will leave nothing to be desired with re- 
spect to exactitude. 
To judge of its extent, we may mention that the temperature of the atmo- 
sphere, and that of the ocean, have been registered from hour to hour, as well 
by night as by day, during the whole duration of the voyage. The barometer 
has been observed regularly, during thirteen months, ordinarily twelve or fifteen 
times a-day ; in other circumstances, from half hour to half hour, or from ten mi- 
nutes to ten minutes.. This multitude of observations will throw some light on 
the mean height of the barometer at the level of the sea, and upon the amount of 
the diurnal periods at a distance from the shores ; that is to say, in circumstances 
where the temperature of the atmosphere varies very little during the 24 hours. 
We shall now also have an opportunity to see if the remark made by Flinders 
at New Holland, concerning the unequal influences which the land and sea 
breezes exert on atmospheric pressure, is equally applicable to the Indian Ocean. 
