APPENDIX NO. 8. TEST OF A TRANSIT MICROMETER. 461 
(3) To determine how many nights of observation will be necessary to secure a 
given degree of accuracy if the transit mirometer is used. 
In a test with these objects in view it was considered desirable to make the condi 
tions no more favorable to the success of the micrometer than would be encountered in 
the field. The test was made for the purpose of discovering possible defects in the 
instrument and method rather than to show what could be done under ideal conditions. 
The conditions during the test were, in the following respects, more unfavorable 
than would ordinarily be encountered in field work. With one exception each observer 
concerned in the test stopped observing before securing sufficient practice to be an 
expert with the apparatus; not one of the observers practiced at all with the instrument 
before taking part in the test; few of the observers had done any astronomic observing 
recently and were therefore out of practice, and some of them had never had any experi 
ence in making astronomic observations. Each time set extended over twice the interval 
it would take in regular work, and hence the errors due to changes in the instrument, 
pier, and rate of the chronometer should be greater than in the regular work. The 
weather conditions were no better than the average in the field, the nights on which 
there was no interruption by clouds being exceptional. 
The observations were all made at the observatory on the grounds of the Coast and 
Geodetic Survey Office. They were made on 18 nights, commencing on March 15 
and ending on May 3. The total number of time sets observed was 75, some of them 
being incomplete sets. A complete set consisted of 10 to 12 stars and included one 
reversal of the horizontal axis of the instrument at about the middle of the set. 
The 16 observers who took part in the work are indicated below in five classes. 
They will be referred to hereafter in this report by initials only. 
Class 1. Observers having experience in astronomic observations and sufficient 
practice within a year in handling some instrument of precision to be in good training: 
E. G. Fischer, Chief of Instrument Division, O. B. French and C. H. Sinclair, 
Assistants. 
Class 2. Observers having no experience in astronomic observations, but having 
sufficient practice in handling some instrument of precision within a year to be in good 
training: W. H. Burger and O. W. Ferguson, Assistants, and F. H. Sewall, Aid. 
Class 3. Observers having experience in astronomic observations, but not having 
had sufficient practice with any instrument of precision within a year to be in good 
training: F. D. Granger and William Eimbeck, Assistants, C. E. Morford, Aid, and 
A. L. Baldwin, Computer. 
Class 4. Observers with little experience at any time in handling instruments 
of precision of such a nature as to be in training for this class of observations: C. R. 
Duvall, R. M. Packard, Delia J. Harvie, Sarah Beall, and Dilian Pike, Computers. 
Class 5. An observer with experience in astronomic observations, but with little 
practice in observing with any instrument of precision within a year. This observer, 
J. F. Hayford, had the advantage over all others in that he did about half of all the 
observing with the transit micrometer from March 15 to May 3, and had, therefore, an 
opportunity which the others did not have to become thoroughly familiar with and 
expert in the use of the transit micrometer. 
The stars observed were all selected from the Berliner Jahrbuch. In the finder list 
prepared at the beginning of the test the stars were designated by consecutive numbers.