1855.] 



NOUVELLES EXPEKIENCES SUE LE MOUVEMENT DE LA TERRE. 



159 



Anglo-Saxon may still wander, as tlie old nomade Indian did, 

 wlien his frail barque bore down tlie Mississippi the inetalli* 

 products of our most northern lake shores ; and by the same 

 highway the prized products of tropical seas were transferred 

 to the regions of our great inland lakes. One opposing element 

 alone interferes with the apparent adaptation of this continent 

 for one vast empire or republic of the future, and that is the 

 elimalotogical variations consequent on the very clement of 

 essential diiference between America and Europe : its extreme 

 diameter extending from North to South. The variations of 

 temperature implied in this, are, as has been noticed above, 

 still further increased by the conformation of the continent ; 

 and in accordance with this we already see nature asserting the 

 influence of her immutable laws ; and while she still facilitates 

 the interchange of the products of the North and South, as in 

 those old times of Indian traffic to which the relics now 

 brought under notice belong, every year seems to increase 

 growing characteristics which so clearly separate the planter 

 of the Southern States from the Anglo-Saxon settlers on the 

 northern area of this continent. 



On the Effect of Pressure on the Temperature of Fusion of 



Different Substances. 



Bij Mr. Hopkins.* 



The author began by stating that it was most fortunate for 

 the success of his researches that, in the very commencement 

 of them he had applied to Mr. W. Eairbairn, who had, with the 

 utmost enthusiasm, entered into his views, and aided him to 

 the utmost extent of the incomparable facilities afforded by his 

 celebrated establishment. jMr. Hopkins then gave a short de- 

 scription of the apparatus which he had used, and the successive 

 steps by which failures in some contrivances had led him to 

 that which were ultimately found to answer. In particular how, 

 from the enormous pressures to which the substances were sub- 

 jected, they found it impossible to use glass to see what was 

 going on within the cylinders in which the substance to be ex- 

 perimented upon was inclosed ; which diflBoulty had been got 

 over by causing an iron ball to rest on the top of the substance 

 within the cylinder; while its presence deflected a small mag- 

 netic needle outside, but the instant the melting of the sub- 

 stance inside permits the ball to fall, the magnetic needle return- 

 ing to its position indicated the fact. The use of this needle made 

 it necessary to make the cylinder of brass ; and Mr. Hopkins 

 stated that with the firstcylindertheyused,!they were surprised 

 to find when enormous pressures were laid on that the liquid 

 within wasted ; the cause of this they long sought to discover 

 in vain, until at length they found that it was escaping through 

 the very pores of the metal in thousands upon thousands of jets 

 so minute as to be almost imperceptible. This they remedied 

 by greater care in the casting of the cylinder, and hammering 

 it well on the outside. The method of laying on the pressure 

 was by a piston well packed and forced down by a lever. This 

 they adopted as the simplest means of getting a numerical 

 estimate of the actual compressing force. — Mr. Hopkins then 

 described the method by which the friction has been determined 

 which opposed the motion of the piston, and so diminished 

 the pressure by so much. This was done by noting the weight 

 required to drive the piston in a certain small distance ; this, 

 less by the friction, was equal to the compressing force ; then 

 noting the weight which allowed the piston to return exactly to 



* British Associntioa for the Advancement of Science, 1854. — 

 Athenccum. 



its first position ; this together with the friction, was equal to 

 the compressing force; but as those two compressing forces are 

 equal, the friction is equal to half the difl'erence of the two 

 weights used, and is then a matter of very simple calculation. 

 Mr. Hopkins then g-ave the results of the experiments, of which 

 the following are the most important : — 



Substances experi- 

 mented upon. 



Spermacetti 



Wax 



Sulphur 



Stearine 



Pressure in lbs. to 

 the Square Inch. 



7,700 11,880 

 7,700 1 11,880 



7,700 

 7,700 



11,880 

 11,880 



emperature Fahrenheit 

 at which it liquefied. 



124° 

 148-5 

 225 

 158 



140° 

 lUG-5 

 275-5 

 155 



176-5° 

 176-5 

 285 

 165 



Of course when the weight was on the .piston, the substance 

 was under atmospheric pressure, or about lofb to the square 

 inch ; and the pressure of 7,79011j per square inch was just that 

 at which the Britannia Bridge had been raised. ]Mr. Hopkins 

 had also tried the metallic alloys which fuse at low temperatures, 

 but had not detected any elevation of fusing temperature re- 

 quired by increasing the pressure ; but these experiments re- 

 quired to be repeated and confirmed before they could be relied 

 upon. 



Nouvelles Experiences sur le Mouvement de la Terre au 

 Moyen du Gyroscope. 



By M. FoucAULT.* 



The author spoke in French, but very distinctly, and the 

 apparatus was'so^simple, beautiful, and exquisitely eonstnicted, 

 that the experiments all succeeded to a miracle, and fully inter- 

 preted the author's meaning as he proceeded. The gjToscope 

 is a massive ring of brass connected with a steel axis by a thinner 

 plate of the same metal, all turned beautifully smooth, andmo.st 

 accurately centred and balanced ; in other words, the axis 

 caused to pass accurately through the centre of gravity, and to 

 stand truly perpendicular to the plane of rotation of the entire 

 mass. On this axis was a small but stout pinion, which seiTcd 

 when the instrument was placed firmly on a small frame, con- 

 taining a train of stout clock-work, turned Ly a handle lUie a 

 jack, to give it an exceedingly rapid rotatory motion on its axis. 

 But to this clock-work frame it could be attached or detached 

 from it instantly. This revolving mass was only about three 

 inches wide, and four of them were mounted in frames a little 

 differently. The first was mounted in a ring, attached to a 

 hollow .sheath, which only permitted the axle and the pinion to 

 appear on the outside, so that it could be laid hold of, or grasped 

 firmly in the hand, if the pinion were not touched, while the 

 ma.ss inside was rapidly revolving without disturbing that mo- 

 tion. By this modification of the gyroscope, the author aflordod 

 to the audience a sensible proof of the determination with 

 which a revolving ma.ss endeavours to maintain its own axis of 

 permanent stable rotation, for upon setting it into nipid rotators- 

 motion, and handing it round the room, each pereon that held 

 it found himself forcibly resisted in any attempt to turn it round 

 either in his fingers, to the right hand or left, or up or down, or 

 in his hands if he signing it round. So that the idea was irre- 

 sistibly suggested to the mind, that there was something living 

 within which had a will of its own, and which always opposed 

 your will to change its position. The second modification pre- 



* British Association 

 Aihmaum. 



for the Advancement of Science, 1854.- 



