310 



Dr. F. Galton. An Examination into the 



two divisions was obtained for the reflection reading. From this an 

 approximate idea of the intensity of the reflected component may be 

 Obtained. Half the total radiation gave a deflection of 120 divisions. 

 The intensity of the reflected component, with a thickness of 45 mm., 

 is therefore 1/ 120th part of the total amount of incident radiation, 

 on the assumption, which is only approximate, that the galvanometer 

 deflections were symmetrical. When the thickness was reduced to 0*3 

 mm., no reflected component could be detected, though the receiver 

 was made extremely sensitive. 



" An Examination into the Registered Speeds of American 

 Trotting Horses, with Remarks on their value as Hereditary 

 Data." By Francis Galton, D.C.L., F.R.S. Received 

 November 29, — Read December 16, 1897. 



It is strange that the huge sums spent on the breeding of pedigree 

 stock, whether of horses, cattle, or other animals, should not give 

 rise to systematic publications of authentic records in a form suitable 

 for scientific inquiry into the laws of heredity. An almost solitary 

 exception to the disregard, shown by breeders and owners, of exact 

 measurements for publication in stud books, exists in the United 

 States with respect to the measured speed of "trotters " and " pacers " 

 under defined conditions. The performance of 1 mile by a trotter, 

 harnessed to a two-wheeled vehicle, carrying a weight of not less than 

 150 lbs. inclusive of the driver, in 2 minutes 30 seconds qualifies 

 him for entry in the Trotting Register, giving him, as it were, a 

 pass-degree into a class of horses whose several utmost speeds or 

 "records" are there published. To avoid prolixity I will not speak 

 particularly of pacers (pace = amble), since what will be said of the 

 trotters applies in general principle to them also. 



The great importance attached to high speed, and the watch- 

 fulness of competitors, have resulted in evolving a method of timing 

 trotters which is generally accepted as authoritative. The length 

 of the track is scrupulously measured, and numerous other con- 

 ditions are attended to, that shall ensure the record being correct, 

 with an attempted exactitude to the nearest quarter of a second. 

 A race against time, even if exact to the nearest quarter of a 

 second, is by no means so close a measure of the speed of a horse 

 relatively to his competitors, as the differential method of ordinary 

 races. The speed of 1 mile in 2' 30'', or of 1760 yards in 

 150 seconds, is equivalent to about 12 yards in 1 second. Now, the 

 length of a horse when extended at full trot is half as long again as 

 his height at the withers — as I gather from the instantaneous photo- 

 graphs of Muybridge — and consequently is hardly ever as much as 



