Translation from the Astronomical Jour. of Hamburgh. 233 
way, as long as the toise itself is yet obtaimable as easily as 
it was at the time of the construction of the meter. 
he apparatus which Mr. H. had constructed for the meas- 
urement of the base line, differs essentially from all that are 
known to me; therefore I will describe it somewhat more 
particularly. The ends of the bars are not planes, but cut 
out, so that viewed from above they present the form 3, 
over this middle excavation the hair of a spider’s web is 
stretched, which therefore indicates the end of the bar: 
over each of the ends a compound microscope is placed, 
which stands upon a separate support, and therefore does not 
change its place when the bar is moved or taken away. 
hen this microscope is placed over the spider’s web, the 
place of the end of the bar is determined by it; the bar can 
then be taken away, and the other end of it can be made to 
coincide with the point where the first had been before seen 
to coincide with the cross strokes of the microscope, which 
in the mean time has retained its position independently. 
the st 
being first properly placed, the microscope is brought to that 
held together by iron clamps: the inclination of this bar to 
the horizon is measured by a sector, nearly as in Delambre’s 
apparatus, When the work is interrupted during the night, 
or, XVI.—No. 2. 3 
