478 
COAST AND GEODETIC SURVEY REPORT, 1904. 
Summary of Conclusions. 
The principal conclusions from this test of the transit micrometer are: 
( i ) That the relative personal equation between any two observers with the transit 
micrometer is so small as to be masked by the accidental errors of observation. This 
is equivalent to saying that it is probably less in every case than o s .o^o, and is as a rule 
much smaller than this. The relative personal equation with a transit micrometer is 
certainly not more than one-tenth as large upon the average as with a key. This con 
clusion as to the relative personal equation applies to inexperienced as well as experienced 
observers. 
(2) The speed of 4.8 seconds per revolution for the driving heads of the transit 
micrometer, for an equatorial star, is the most favorable for accuracy, or possibly a 
slightly slower speed. 
(3) Very little loss in accuracy will result from reducing the number of records per 
star from 36, as in the present instrument, to 20. Such a reduction should be made to 
save time in reading the chronograph sheets. 
(4) It is predicted that three nights of observation with a transit micrometer and 
without exchange of observers will probably secure the same grade of accuracy as has 
been obtained from ten nights of observation with a key, and including an exchange of 
observers. Each night of observation is supposed to include two time sets, or 20 stars 
for each observer. 
Aside from these conclusions the following items of information secured during the 
test are interesting and important: 
1. For a practiced observer with a transit micrometer, the total error for a star, 
including errors which are constant for all the records as well as the accidental errors of 
bisection, is for the slower speed of the driving heads nearly the same for stars of all 
declinations, if expressed in angular measure. This is what should be expected if the 
errors concerned are of the same nature as if the object pointed upon were stationary 
instead of being a moving star. 
2. For both the speeds used and for a practiced observer, the accidental errors of bisec 
tion are nearly the same, expressed in angular measure, for stars of all declinations up 
to 58°, and are probably somewhat less for stars of greater declination. This is an indica 
tion that the accidental errors of bisection are of the same nature as if the image 
pointed upon were stationary, the conclusion being partially contradicted by the smaller 
errors for stars of declination greater than 58°. 
3. Good observations can be secured at once with the transit micrometer without 
previous practice. More practice simply reduces the accidental errors by about 25 per 
cent. 
4. One incidental advantage of a transit micrometer not commented upon hereto 
fore in this report is that the observations may be made much more rapidly with it than 
with a key. With a key about ten stars per hour may be observed conveniently. 
With a transit micrometer sixteen stars per hour can with equal convenience be observed. 
The list used during this test contains sixteen stars per hour. This advantage results 
from taking all the observations for an equatorial star in less than ten seconds instead 
of scattering them over an interval, for instance, 30 seconds or more, when observing 
with a key.