A descriptive list of anthropometric apparatus : consisting of instruments for measuring and testing the chief physical apparatus of the human body : designed under the direction of Francis Galton, and manufactured and sold by the Cambridge Scientific Instrument Company.

Date:: 1887

Credit: A descriptive list of anthropometric apparatus : consisting of instruments for measuring and testing the chief physical apparatus of the human body : designed under the direction of Francis Galton, and manufactured and sold by the Cambridge Scientific Instrument Company. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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$iustruincnt the attendant releases the rod by turning a milled head at the top of the instrument; this is carefully arranged to make no sound. The signal sound is given after the rod has fallen a definite distance by a weight which rests on the top of the rod being caught by a diaphragm. If a sight signal is required this weight is removed and the instrument is placed so that a bright light can be seen through a small aperture; the falling of the rod closes this aperture after it has fallen a definite distance. The depression of the key releases a catch which gi'ips the rod firmly and brings it to rest. As it is impossible to destroy the momentum of the rod suddenly, an arrangement has been devised which reduces the error from this cause to an infinitesimal amount. An arrangement can be applied by means of which an electric circuit is broken at the moment the signal is given. Also an arrangement by means of which the catch for gripping the falling rod can be released by the breaking of an electric circuit. By these means the instrument can be used to measm-e the reaction time from an electric signal. It can also be worked from a distance which in some cases would be useful. The maximvim period of time that can be measured by this instrument is three-tenths of a second. It is proposed to design an instrument which will be able to measure a greater interval of time than three-tenths of a second. See On Apparatus for testing the Delicacy of Muscular and other Senses in diflPerent Persons by Francis Galtou, F.R.S. Journal of the Anthropological Institute, May 1883. The instrument consists of a box containing ten trays which can be easily removed. Each tray contains three weights, identical in size and appearance but differing in weight from each other. The three weights in each tray form a series of gradually increasing weights, and the series in each tray differ in value. The weights form a geometrical series, thus :—Ifr, Wr\ Tfr^, Wi^, &c. It follows from Weber's law, that if a person can just appreciate the differences between two consecutive weights in this series, he can then also just appreciate the difference between any other consecutive pair. The values adopted are lf= 1,000 grains and of ?*=1-01. The following are the values of the weights in each tray. Appreciation of slight differences of Weight. Tray No. 2 contains weight Tr;-«, Wr% TTV». 6 „ „ nvo, Wr\ 7 „ „ Wr\ Wr\ 1IV». 8 „ „ ]|>io, 1IV18.$