Frenéh National Inflitute: Reg 
aftar, ora planet, as almoft to eclipfe it. They obferve 
thefe phenomena with great care, becaufe they can deduce 
from them, with fufficient precifion, the errors in the lunar 
tables. The ConnoifJance des Temps, An. VI. announced 
an occultation of Mars vifible at Paris. The diftance be- 
tween Montauban and Paris was fufficiently great for the 
Moon to appear in the latter a little higher than Mars, and 
confequently not to produce an occultation of the latter. 
This obfervation gave Cit. Duc an opportunity of examining 
with attention the difk of Mars; and he obferved, in the 
auftral part, a {pot of a very fenfible diameter, round and 
white; a colour very apparent on a planet the appearance 
of which is reddifh. According to fome other obfervations 
which he made afterwards, Cit. Duc eftimates that this {pot 
is fituated at the pole of the planet. 
A paper was read in the fitting of Meffidor 15, in bias 
Cit. Delambre gave an account of the operations for 
meafuring the firft bafe from Melun to Lieufaint, extending 
in length 11808°5 metres. A fecond bafe has juft been ~ 
meafured on the high road from Perpignan to Narbonne. 
The length was found to be 11702°6 metres. Rarely have 
bafes of fuch a length been meafured, and {till more rarely 
has it been found poflible to place them on ground fo fmocth 
and fo level. But however regular the roads chofen for 
thefe operations may have been, there occurred in. them a 
bending almoft imperceptible to the fight, and which 
rendered it neceffary to break the two bafes. In this man- 
ner, inflead of meafuring a ftraight line for each bafe, two 
were meafured, forming an angle of _ 80° of the ancient 
divifion. The excefs of the broken line over the ftraight 
liné to Melun did not exceed 27 centimetres, and not more 
than 6 at Perpignan. The new bafe was meafured with the 
fame rules of platina which ferved at Melun. The difficulty 
of tranfporting, without any accident, inftruments fo de-— 
licate, along fo lengthened a route as that from Paris to 
Perpignan, and the neceflary preparations and local diffi- 
culties, 
