10 SEC. 1. ARITHMETIC. 



46. Cavendish's Original Counting Machine. 



Council of King's College, London. 



47. *' The Motometer," a machine to indicate the number 

 of revolutions made per minute, or other portion of time, by a 

 steam engine or revolving shaft or other body having intermittent 

 motion, so that by simple inspection of a dial the rate of speed may 

 be seen. H. Faija. 



This instrument is constructed so as to indicate by a positive 

 motion direct from the engine or other moving body to which it 

 is attached, and is of purely mechanical construction independent 

 of all centrifugal and other forces of an indirect nature. The 

 indication is consequently absolute and not comparative. 



The instrument is made in four different forms according to 

 requirements ; for instance, 



No. 1 is intended for slow motions, as in pumping engines, &c., 

 where each separate revolution is indicated. 



No. 2. For all ordinary marine and stationary engines with 

 speed varying from 20 to 100 revolutions per minute, in which case 

 the speed is indicated at every tenth revolution. 



No. 3. To indicate extremely high speeds, such as locomotives, 

 &c. 



No. 4. To indicate at the tennination of each minute the exact 

 number of revolutions made during that minute. 



The machine exhibited is No. 2, being the form adapted to most 

 general purposes. 



III. MISCELLANEOUS. 



48. Apparatus for the Statistical Treatment of large 

 numbers of Seeds, &c., to sort them rapidly into classes 

 differing by regular gradations of magnitude, with the view of 

 testing how far the relative numbers in the several classes accord 

 with the results of the. Law of Error or Dispersion. 



Francis Galton, F.R.S. 



It consists of a box, with bars parallel to one another, and having a bevelled 

 edge, fixed horizontally across its top. There is also a frame of other bars, 

 held together like those in a gridiron, that lie on the top of the box between 

 these. Consequently, when the frame is pulled forwards as far as it can go, 

 each of its bars closes along its whole length against one of the fixed bars, 

 and when it is pushed gently back the framework bars separate simultaneously 

 and equally from the fixed bars, and any objects that may have been laid in 

 the bevel between their edges, and are small enough, will drop through. The 

 framework is moved by a screw turned by a ratchet wheel, which is itself 

 moved by the to-and-fro action of a handle between stops, one of which is 

 adjustable at pleasure. Hence, every time the handle is worked, the space 

 between the bars is widened by a definite space, and all the seeds, &c., whose 

 diameter is greater than the original and less than the final space, will drop 



