SCIENCE. 



>ue, in the ceiling of the dome, where it again enten the 

 C'uiioitit copper railing, and descends as before. The ball con- 

 tinues this motion with the greatest regularity, perform- 

 ^ v ^" ing its ascent and descent in equal times, and conse- 

 quently communicating an equal motion to the clock in 

 the pedestal below, by its successive impulses upon 

 the spring beneath the hoh- 1 1 



In another clock of the same kind, the small copper 

 ball, in place of being projected upwards by a spring, 

 is carried upwards in a small bucket which rises and 

 falls perpendicularly within the columns. This little 

 bucket receiving the ball when it quits the wire 

 groove, delivers it into the dome at the commence- 

 ment of the railway. 



In a third clock the copper ball is carried up on the 

 outside groove of an Archimedes's screw placed in an in- 

 clined position between the columns. In a fourth 

 clock, which resembles a writing desk, a second bail 

 makes its appearance at the top of the railway just 

 when the first descends into its hole, and these two 

 balls succeed each other with great accuracy. 



In aji/th clock the copper ball passes through the 

 bodies of two serpents, one placed above the other ; 

 the upper one having a see-saw motion' round its cen- 

 tre. When the upper serpent stoops with its head it 

 receives from the tail of the lower serpent a ball of 

 copper which it swallows, and passing along to its tail, 

 the descent of the tail delivers it into the mouth of the 

 lower serpent. The oscillations of the upper serpent 

 give motion to the clock in the pedestal below. This 

 Fig. IS. c i oc k J 8 shown in Plate CCCCLXXXV. Fig. 13. 



In a sixth clock a cylindrical copper box, about five 

 inches in diameter, with dial plate and hour hand like a 

 watch, descends imperceptibly along an inclined plain. 

 There is also a rectilineal dial with the hours on the 

 edge of the inclined plane ; and the index hand on the 

 cylindrical box, which always keeps a vertical position, 

 points out with its upper end the hour on the dial of 

 the box, and with its lower end the hour on the recti- 

 lineal dial. This timepiece has neither spring nor 

 counterweight. The time that it keeps going is pro^ 

 portional to the length of its inclined plane, and it re- 

 ceives its motion only by the effort which the round 

 box makes to retain itself on the inclined plane con- 

 trary to its natural tendency downwards. The expe- 

 riment with it is made thus : when the box is on the 

 inclined plane it descends imperceptibly and regularly, 

 marking the time as has been mentioned, and the mo- 

 tion of its balance is distinctly heard ; but as soon as 

 the cylindrical box is taken from the inclined plane 

 and placed on a horizontal plane, the motion of the 

 clock ceases, and the sound of its balance is no longer 

 heard, because the round figure being then in its na- 

 tural state no longer makes any effort. 



In a seventh clock the cylindrical box after com- 

 pleting one inclined plane comes upon a horizontal 

 one which it elevates to the same angle as the rirst ; 

 and in an eighth clock the inclined plane forms a spi- 

 ral round a little temple, the inclined plane replacing 

 the wires in Fig. 12. and the box takes a week to 

 descend it. When it has reached the bottom it is car- 

 ried up to the top and again commences its descent. 

 *and clock. Another clock described by M. Serviere operates by 

 the fall of sand, which causes it to move. The flow of 

 the sand occupies exactly one hour. Its cage has an 

 axis round which it turns like the index of the dial of 

 a common clock. The two glasses which hold the 

 sand have the form of those in the common sandglass. 

 They have each a false moveable bottom, which can 



Clodu 



rieand fall a little by the aid of a fine p : ece of skin 

 which folds up and falls down like the leather of a pair 

 of bellows. When the sand has flowed from the upper 

 into the under glass, the false bottom of the hut glass, 

 on which all the sand rests, descends and presses up a 

 lever balanced by a counterweight leu heavy than all 

 the sand. The beam, therefore, receives see-taw 

 motion at the moment when the last grains of sand fall 

 into the lower glass, and a detent being at the same 

 time loosened, the springs in the interior of the box 

 act and turn round the sandglass. The empty bottle 

 is now undermost, the sand again flows, and the MUM 

 operation is repeated. Every time that the tandgla** 

 turns, the dial plate, which is within the box, makes one 

 twelfth of a revolution, and each hour shows itself at 

 an opening in the box. 



In another clock of M. Serviere's invention, the 

 hours marked on the horizontal cornice of a room are 

 pointed out by the figure of a mouse which runs along 

 the cornice, . ml the same effect is produced on a ver- 

 tical column by the ascent and descent of a lizard. 



The last clock of M. Serviere's invention which we 

 shall notice, consists of a plate of tin like a soup plate, 

 on the circumference of which the hours are engraven. 

 After filling the plate with water, a tortoise cut out of 

 rork is thrown into the plate, and constantly goes in 

 quest of the hour, pointing it out with its mouth 

 on the dial-plate. When left in that position it fol- 

 lows imperceptibly the margin of the plate, showing 

 the hour with great accuracy. In whatever way the 

 plate is turned, and wherever it is placed, the tor- 

 toise indicates the hour with equal accuracy. The 

 construction of this piece of mechanism is not hinted 

 at by M. Serviere, but we cannot doubt that there is 

 placed in the inside of the plate, that is, within the 

 thickness of its bottom, a common watch, whose hours 

 correspond with those on the external dial, and whose 

 hour hand is magnetised. If a piece of steel or soft 

 iron is placed within the tortoise, it is quite clear that 

 the magnetised hour hand will cause the tortoise to 

 take a parallel position, and to follow it round the 

 dial-plate, pointing out the hours with the same ac- 

 curacy as the real hour hand would do were k vi- 

 sible. 



There are a great many amusing and highly inge- 

 nious pieces of clock-work invented by Dr. Franklin, 

 James Ferguson, and others, which might with great 

 propriety have been described in the present article ; 

 but as most of these have been described in the works 

 of Ferguson, which are in the hands of almost every 

 person, it would not be adviseable to repeat the des- 

 criptions here, as our object has been to describe in- 

 ventions which are not very commonly known, and 

 which are found in works not possessed by general 

 readers. 



HYDRODYNAMICS. 



In our article on HYDRODYNAMICS, we have given 

 an account of various amusing experiments, to which 

 it is necessary only to refer the reader. 



1 . Mr. Perkins's Steam Gun*. 



Among the most remarkable inventions of modern Mr. Per- 

 times, must be enumerated the steam gun of Mr. Per- ' 

 kins, by which, with the elastic force of steam, he is 

 able to discharge balls with a velocity and force which 

 surpass even those produced by gun-powder. But 

 it is not merely on this ground that the steam gun 

 is superior to the ordinary one. The balls may be 



