206 SNYDER — A NEW METHOD OF TRANSITING STARS. [April 4. 



an entirely novel and highly suggestive method for its elimination 

 in many classes of observation. And it may therefore be .permis- 

 sible, in this presence, to draw attention to the fact that the 

 method of the electrical transiter permits for the first time the de- 

 termination of the absolute personal equation at any and every de- 

 sired star transit, and on the star itself. While reserving a com- 

 plete discussion of this subject for a future occasion, it should be 

 stated that several plans offer themselves to this end in the transiter. 

 To mention but one : The usual wires are undisturbed, and the 

 transiter can be adjusted so as to cut itself in and out automati- 

 cally at certain parts of the run and only there receive the at- 

 tention of the observer for star-bisection. At other portions of 

 the run the usual method of chronographic signals, or even of the 

 eye and ear method may be employed, and so, on reduction to the 

 middle, be compared with the transiter's automatic signals. Per- 

 sonal equation may thus be studied with facility on the stars 

 themselves and its variability traced through a simple observation 

 or a series of observations, and whatever is sufficiently stable ex- 

 pressed as a function either of the stellar declination or of stellar 

 magnitude or even of the physical condition of the observer. 



It seems rather likely that finally all such study of the personal 

 equation, when it shall have clearly demonstrated the unreliable 

 character of the usual methods of transit observation and the ade- 

 quate accuracy of the newer method, will be relegated to the 

 Psychological Laboratory. Certain it is that the banishment of 

 reaction time from transit observations and the reduction of this 

 class of errors to those of bisection, either of a star image by a 

 thread or of a thread interval by a star, means an epoch in ob- 

 servational astronomy whose actual realization by suitable devices 

 is a worthy challenge to our best efforts. 



With an automatic transiter allowing easy and accurate bi- 

 sections, a chronograph recording with the utmost accuracy, and a 

 clock of the best mechanism kept under constant pressure and 

 temperature, a new field for accurate work in longitude determi- 

 nation and in the evaluation of stellar position and stellar parallax 

 would be opened to the activity of the astronomer. 



Philadelphia Observatory, March, 1902. 



