36 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



correcting such observations, and the effect of rejecting them, three 

 additional sets are given in Tables III, IV, and V. The first is that 

 of Brookins on September 10, in which he reached the greatest altitude 

 of the meet, with three discordant observations, one of which has been 

 corrected, apparently with reason, by altering the vertical angle at the 

 Quincy station by 1°. The others would be brought into line by 

 changes of lo' and 30' in the vertical angles at Milton station, but no 

 outside evidence is furnished by the sextants or spiral to justify such 

 a change. In both cases the spiral, Figure 5, indicates that the hori- 

 zontal angles were probably correctly recorded. 



.woo 



4.500 



40O0 



a.'ioo 



oooo 



2.-iOO 



2000 



1.500 



lOOU 



000 



;jo a."> 10 



n () 



JO 15 ;io 



Figure 4. Flights of September 10: Brookins (Wright biplane), Grahame- 

 White (Farman biplane). 



The second flight, that of Brookins on September 8, shows two cor- 

 rections of vertical angle and one change of the time of observation at 

 Quincy, three vertical angles unrecorded at Milton, and one observa- 

 tion marked worthless, the result from which differs 17 feet from that 

 at Quincy. This was on the second occasion of making observations. 



