156 
fammer. This phenomenon may depend 
either on the imperfect knowledge of ab- 
folute. refraction, cr of the variations 
which it experiences in different ftates of 
the atmofphere. ; 
- CC, Lecenpre has given a third edition 
of his Georsetry; and C. Lacroix a fe- 
cond of his Elements of Algebra. The 
quick demand for thefe works fhews both 
their real merit, and the zeal with which 
mathematics are ftudied in France, 
The Executive Commiffion of Pied- 
mont, who have received from C. Va4- 
SALI the models of the metre and the ki- 
logramme; write to the Inftitute, that 
they are about to appoint a Committee in 
order to eftablifh, with the greateft accu- 
racy, the relations between the weights 
and meafures of Piedmont and. thofe now 
adopted in France. It will alfo do its 
utmoft to make the people fenfible of the 
advantages of the new metrical: fyftem, 
the adoption of which will add to the bonds 
of union which fhould fubfift between the 
two nations, 
The INSTITUTE of CAIRO 
Have been publifhing fome of the refults 
of their labours. Among thefe are the 
following :—.. 
A Memoir of C. Lancret and‘ Cua- 
BOL on ‘the means of re-eftablifhing the 
canal of Alexandria, which will be no lefs 
ufeful a work to agriculture than to com- 
merce. 
A Table of the Longitudes ‘and Lati- 
tudes of different points of Upper and 
Lower Egypt, by C. Novet, and the 
obfervations of the fame aftronomer to de- 
termine the courfe of the Nile from! Syene 
to Cairo. This is anew and important 
work, which has been carried on with the 
greateft exaétnefs. 
A Memoir by C. LEPERE on the Mehyas 
of the Ifle of Raoudah, a monument con- 
ftrucied by the Caliph Almanon, in the 
year 215 of the Hegira, to meafure the 
height of the Nile. It confifts of a well, 
which communicates by- a fubterranean 
paflage with that river, and therefore the 
water which it contains is always on-a 
jevel with thofe of the Nile. In the mid- 
die of the well is a marble column divided 
into cubits, palms, and digits, for a feale 
of height. For the convenience of the ob- 
ferver winding ftairs are fixed to the fide 
of the well, down to the bottom. And 
when the French came, that well was 
Nearly filled with the flime of the water, 
fo that the communication with. the river 
National Inftitute—Inftitute of Caire. 
[ Match y, 
was only kept up by filtration C. Le- 
pere has caufed it to be thoroughly cleaned 
out, and thereby the column has been 
completely expofed, and the divifions on 
the fcale are found to be more accurate 
than has been imagined. The fize of each 
of the fixteen cubits is .54 of a metre— 
(about 21 inches Englifh.) 
Laftly, a long Memoir upon the agri- 
culture and commerce of Upper Egypt, by 
C. GirarpD,. which concludes in thefe 
words :—** What fuccefs may not be 
looked for from all that has been under- 
taken for the amelioration of Egypt, whichs 
placed in the centre of the old world, may’ 
unite all its produ&tions, and from the 
advantages of its fituation become the. 
moftnatural emporium forthe commerce of 
the univerfe ?”’ 
2 
* 
SOCIETY Of EMULATION af ROUEN. 
Cit. Poucnet propofed a method of 
afcertaining with exaétnefs the degree of 
finenefs of cotton. ‘* The finenefs of 
thread,"” he fays, ‘* is expreffed by their 
length in a given weight ; thus at Rouen 
the thread No. 24 meafures. 2400 ells” 
in the pound. The fame rule may be-ap- 
plied to the raw cotton, taking fmaller ad- 
meafurements in order not to raife the 
numbers to an inconvenient height. Thus 
in eftimating the finenefs of No. 20 of 
the Fernambouc and Bourbon threads it 
is found, that the numiber of hairs which 
go to form the thicknefs of each, is 68 in 
the former, ‘and 120 in the latter. Now 
as the No. 20 indicates 20,000 ells in the 
pound, it follows that there are 1,360,000 
ells of hairs in the poundof Fernambouc, 
and 2,400,000 in the Bourbon, which - 
numbers may be expreffed by 33 and 58 
refpeétively, the former ‘of which is the 
number of hectometers ina gramme. This 
general method is applicable to wool alfo, 
and therefore in {peaking of the different 
forts of this article, fuch as that of Spain, . 
England, Berry, &c. a more accurate idea 
of their comparative finenefs will thus be 
formed, and the labours of the manufac- 
turer will be directed with more precifion.”” 
To this plan of Pouchet, the objection 
was urged that, ‘* if the Bourbon is finer 
than the Fernambouc, ‘and if finenefs is 
to be the leading diftinftion in the value 
of the article, how happens it that the 
Bourbon is confiderably cheaper than the 
Fernambouc and other: kinds which are 
inferior in this quality ?’’ To this the au- 
thor of the paper replies, that the Bour- 
bon has realby a quality and intrinfic value | 
fuperioy 
ee ta eed Be 
