Preside7itial Address. 
423 
a battleship, who keeps his gun continually pointed on a moving target, 
so that a hit may be secured at any moment the gun is discharged, say, 
from the conning tower of the ship. 
A more recent innovation has been the introduction of a mechanical 
method of driving the moving wire at a speed which could be adjusted to 
correspond with that of the apparent motion of the star in the field of the 
telescope, and to provide means by which the observer could instan- 
taneously bring the web into exact coincidence with the moving star. If 
the speed adjustment is then exact, no further action on the observer's 
part is necessary, but if inexact he is able to correct the movement from 
time to time in the course of a transit, the results involving such correc- 
tions being automatically recorded by the self-registration method on the 
chronograph. 
The new Transit Circle of the Cape Observatory, the erection of which 
was commenced in 1901, was designed to be operated by the methods 
which I have been endeavouring to explain to you. 
Owing to the necessity for the completion of earlier programmes and 
the time requisite for preliminary investigation of the instrument, it was 
not until the beginning of 1905 that a regular observing programme with 
this instrument was begun. Even then the instrumental equipment was 
not complete. The earlier attempts at providing a satisfactory mechanical 
movement for the travelling wire had not proved successful, and it was 
therefore necessary to commence with the use of the hand-driven web. 
The programme of work was, however, so arranged as to bring out the 
capabilities of this method when pushed to its highest refinements. 
The immediate object of this programme was the formation of a 
fundamental catalogue of a selected series of stars. This required not 
only that the observations should be made with the highest precision 
attainable, but that they should be so arranged as to be self-sustaining in 
all respects, i.e., that they should not be made to depend on existing 
almanac data, but should rather be available for improving them. It w^as 
judged expedient to push the working programme to completion by the 
methods under which it was begun before proceeding with further experi- 
mental work. With the exception of a short interruption in the course of 
the year 1907, this occupied the observing staff until the end of the 
year 1910. 
In the meantime, however, an improved driving apparatus was designed 
and constructed. This was readily adapted to the instrument, and brought 
into experimental use from the commencement of the year 1911. Special 
devices, to which I shall refer later, were included to overcome some of 
the difficulties met with in the earlier experiments. 
Now I wish to call your attention to a few of the results obtained in 
gelation to personality in determining time or clock error. 
