20S Description of the Newcastle Dijnamometer. 



strain on the rope might be read off at any time. In passing, it 

 may be mentioned that no force on the rope would ever raise the 

 pulley M to /*, or place the three pulleys A, M, and. B in a 

 straight line. Such are the leading principles in the dyna- 

 mometer shown in the engraving. 



In experimenting upon the force required to work field-imple- 

 ments, it is found that from numerous causes the resistance is 

 ever-varying, and the observer has much difficulty in determining 

 the average or mean force employed, because an index placed as 

 at the pulley M continually shifts with the resistance. To over- 

 come this difficulty, contrivances have been resorted to, most of 

 Avhich have obtained the results in too complicated a manner for 

 general use in our experiments. 



To our French ncighl)ours we are indebted for an invention 

 called the " Totalisateur," a machine which enables us to obtain, 

 in a simple manner, answers and results which before its intro- 

 duction involved tedious and lengthy calculations. 



The princij)le of the invention mav be thus briefly explained. 

 The machine may be said to consist of two parts ; the first has 

 a progressive motion imparted to it corresponding in some exact 

 ratio with the progression of the implement on trial, and it is 

 provided with a counter which affords the means of recording 

 the exact distance which the implement has travelled ; and so 

 far is simply a " perambulator " for measuring distances. One 

 of the principal features in this part is a " disc-plate," having a 

 plane surface, and to that " disc-plate " the motion before spoken 

 of is given. 



The second part consists of arrangements for determining the 

 resistance caused by the implement, and this is effected by a 

 small " disc-icheel " carried on centres, as will be hereafter 

 fxplained (Fig. 4). The edge of it is placed lightly in contact 

 with the plane face of the "disc-plate" before-mentioned, and 

 thus by means of rolling friction, the revolution of the plate will 

 cause the ''^ disc-tckecV to turn, except when the edge of the 

 '■^ disc-ioheel" is in the centre of the "disc-plate." The adjust- 

 ment is such that the disc-wheel occupies this latter position 

 when there is no resistance from the implement ; but as resist- 

 ance takes place, the " disc-irheel " is moved from the centre 

 towards the periphery of the " disc-plate," to a distance which 

 increases with that resistance ; as the resistance decreases, the 

 wheel returns again towards the centre, and whatever position 

 the " disc-wheel " may be in when removed from the centre, a cir- 

 cular motion will be imparted to it by the "disc-plate," with a 

 velocity depending upon its then distance from the centre of that 

 plate : hence it will be seen that the velocity of the " disc-wheel " 

 will correspond with the amount of resistance of the implement. 



