56 
REPORT—1854. 
General Physics. 
On the Density of various Bodies when subjected to enormous compressing 
Forces. By YV. Fairbairn, C.E., F.R.S. 
The author briefly explained the apparatus which lie made use of. ami gave a 
sketch, ot the results at which be had arrived; but as these were almost entirely 
given in tables, we are unable to detail them without the aid of these, which are to.', 
vo uminous for insertion in full. Among other matters of extreme general interest, 
V? „ that ' ,'" 8k1cs ™« 8e common pressures of 7000 lbs. to the square inch, and 
n non . SU ? h M Uscd 10 Mr - Hopkins's experiments, he had applied pressures of 
°,°00 lba. and 90,000 lbs. to the square inch, or what would be equivalent to the 
weig 1 of a column of water over 33 miles in height. Under this enormous pressure, 
clay and some other substances hud acquired all the density, consistency, and hard- 
ness ol some of our hardest und densest rocks. 
Nouvelles Experiences sur le Mouvcmtnt Je fa Terre au Moyen du Gyroscope. 
By M. h. Foucault, Paris. 
1 ' n [V l “ thor 1 s f >0 * {e . '. r ‘ french, but very distinctly, and the apparatus was so simple, 
Beautiful, and exquisitely constructed, that the experiments all perfectly succeeded, 
anu fully interpreted the author’s meaning as he proceeded. The gyroscope is* 
massive ring of brass connected with a steel axis by a thinner plate'of the tame 
e a , a turned bonutilully smooth, und most accurately centred and balanced; in 
o er words, the axis was made to pass accurately through the centre of gravity, and 
nvU y to the plane of rotation of the entire mass. On tins 
f. . “ ® ma } bul 8tout pinion, which served, when thu instrument was placed 
k^a Sl fr “ m °’ Contai . nin g a train of stout clock-work, turned by a handle 
clock work ''V nu , ®* Ccc dingly rapid rotatory motion on its axis. But to tires 
b ? Uetachecl from it instantly. This rcvolvmg 
Ki: about a inches Wide, and four of them were mounted in frames* 
;^ dl , nty '. r,lt ‘ ,lrst w as mounted in a ring, attached to a hollow sheath, 
Sid belli Stn the telB aod ** plntol to nppoar on the outside, so that n 
while the ,n„ h ° ' °V ,r gras,Hd firm, y i'> the hand, if the pinion were not touched, 
this n r IB f* TO ra P it]I y revolving without disturbing that motion. > 
proof of*UiTdon. of gyroscope, the author afforded to the audience a sens,b 
Swn wia ?f n^rL , W,th whicb a revolving mass endeavours to maintain its 
ami hamUnf i- “ "‘fh' 6 rotatiou i *'» upon setting it into rapid rotatory motion. 
?es sted i ‘"L n » 0Um th0 r ° orl, ‘ Person that held it found himself forcibly 
or ui oVjown n T P l'° ! Um il rouud in his fingers, to the right hand or left 
Suw? suScJ £*! h “ d \ if be swu 'ig it round ; so that the idea was ^ 
will of its^own and JhicT” 1 ?’ lmt thcre wa ® something living withur which h 
second modification » ‘ al , W f ys opposed your will to change its position, [> 
335d Sfth SSiETS** 11 »■» suspended it, a stout ring, which was £ 
placed in a .m3?S2 S'*' bke thc ™g of the girubal. These axles could he 
on a piece of smooth?.^ ? ood bushed with brass. This small frame, when p 
ho^on wtochT i^, CuU,d be tor.K-d freely round by turning the P*c«« 
sufficient to cw. i iff n ? ' 0 ° S ah the BJ^ope was not revolving, friction beg 
rapidly retoSr n t ° 1° t0rn with ,ba but, when the gyroscope! «■* 
Which it rested^ SO • ° U at | cm Ptcd to turn the frame, by turning the boar 
rotaUon did * endeavour to maintain its own 
scojrc it’was susocude,?? 0 '^^ 11 ! 0 fr,clion - In the third modification of thegj 
scope proper and the f° cxt l u ' s ‘toly constructed that both the 1 g) 
freely when placed in an/Slf® R - ,niba t ls wcro accurately balanced, so as ^ 
showcrl THAtt . In , a 7 P°-*ition in relation to the earth. Bv this the au ' 
