A 
_ If in place of putting the knife blades on the agate plates, we insert 
the points of the screws, q, q', which carry the axis of the torus, by 
which all movement of inclination in the inner circle is prevented, we 
: ich 
Parallel to the axis of the diurnal rotation of the earth, so that the direc- 
tion of the movement of the torus is the same with that of the diurnal 
iin: 
_ This apparatus M. Foucault calls a gyroscope, and by its aid we may 
find the pole, and the east and west points, determine the latitude of a 
Place, and study the rapidity of the earth’s motions, without recourse 
either to astronomical observations, the magnetic needle, or a pendulum. 
The apparatus has. been admirably constructed by M. Froment. Other 
capable mechanicians had given it up; but it proved mere play to this 
“stinguished artist who bas so largely extended the limits of precision in 
Philosophical instrumehts. We shall more than once entertain our read- 
. with the apparatus, and especially, the,electro-magnetic machines of 
55 Froment. Everything connected with electricity is manufactured in 
Sestablishment, and it is a treat to gain access to his private apart- 
ments where. there are all kinds of electro-magnetic machines, and 
bom some whose electro-magneis make 12,000 inversions per 
_ Influence on Astronomical Observatories of vibrations produced by 
Passing on roads, and other causes.—The Paris Observatory 
(ane Toads, have for a long time been observed, and they have inter- 
“ with their observations, especially those made with the aid of re- 
on rom ame i These difficulties, which have been 
by all astronomers who have observed in circumstances like those 
Yais, ris, came under the consideration at the same time of M. Ma 
hoes, ‘ma small but elegant observatory constructed at the centre of 
buildings of the old abbey of Fontenay, near Montbard, and close 
a Planning, unbeknown to one another, a method of overcoming 
: difficulties, M. Mauvais happened to pass by Montbard, and meet- 
aa >eguin, mentioned to him his project; and since then they have 
mn, United in their endeavors, and have hit upon an extremely simple 
od 1. °F Protecting the mercury from external vibrations. The meth- 
“tha 5° take a strap of vulcanized caoutchouc, fold it double and fix in 
Pg >that is, at the middle of the band, the stand which supports 
™ercurial horizon ; then attach a cord to each end of the strap and 
