Show A scientific INVENTION an which be boril the ubera carleton Cari eton college observatory has secured a curious instrument invented by a scientist at washington and called a personal equation machine says a northfield letter to the st paul pioneer press the object of the instrument is to harmonize the observations of different persons who aro working together at different times or at the samo time astronomers well know that no two persons see exactly alike by which is meant for example no two persons will say that a star passes a wire in a telescope at exactly tho same instant one will record its apparent passage slow on true time while another will almost uniformly put its time fast observers unconsciously form a habit of seeing objects baat or slow on true time and the bettor the observers the more steady this error is as compared with true time this error the astronomer calls the personal equation of the observer in amount the personal equation varies from 03 of a second of time to something more than half a second for different observers either fast or slow on true time kiich errors as these can not be tolerated at all in astronomical observations lor fundamental or original work of a nice kind but must be in some way eliminated befaro final reductions can bo attempted to accomplish this way an ingenious machine has been constructed which sola in motion an artificial betar quite like tho appearance of a real star in tho telescope As this artificial star passes wires in the machine er records and the instrument ment automatically records the exact time of the real passage of the star over the wire now both records are mado by tho aid of the electric current and consequently are perfectly ruo these records arc taken automatically in ink on an instrument called a chronometer and hence their differences can be measured with tho utmost accuracy and in this way the error of the observer on true time is satisfactorily known the machi aei ia in use every highs that observers work either together or singly so that changes in individual personal equations may be detected as well aa the differences that may exist between observers the instrument therefore furnishes standard for accurate rr ayon rs r L i i |