163 LOWELL— SUPPOSED SIGNALS FROM MARS. [Dec. 6, 



6. The opposition of 1894 was very prolific of projections, over 

 four hundred being seen at Flagstaff in the course of nine months. 

 The next opposition was not so good ; while in that which has just 

 passed, that of 1 900-1, only two were detected. It was these two 

 which gave rise to the notion of signals from the planet. 



Now the variability in the number seen at different oppositions 

 should have materially shaken faith in the mountain explanation. 

 Mountains are permanent affairs, and if they be high enough to 

 catch tha light and show as protuberances at one time they should 

 do the like at another. The change in the inclination of the disk 

 would not materially alter their visibility. But it is one of the 

 humorous anomalies about human nature that general reasoning 

 affects minds so little when applied to unfamiliar matters, while in 

 familiar ones it is the guiding principle of life. 



7. Argument from the two projections of the last opposition is, 

 on the other hand, particular. Although they were but two in 

 number, testimony in the case is very much to the point. Indeed, 

 their isolated character helps to make their cogency the clearer. 



On December 7, at i6h. 15m. S. M. T., Mr. Douglass suddenly 

 noticed a projection on the terminator of the planet, a little to the 

 north of the Sabaeus Sinus. The phase loss at the time was 36°.4. 

 As he continued to watch it the projection increased. The distance 

 of its tip from the edge of the terminator passed successively 

 through the values y/3, 1, 1^3 and 1% of a thread; the thread used 

 being the stationary spider's thread of the micrometer. Meanwhile 

 he was busy taking the position angle of the tangent to the termi- 

 nator, at the point directly under it, at intervals of a few minutes. 

 His observations, recorded in detail in the observing book, are as 



follows : 



Record of December 7, 1900. 



Th. = thread ; P. A. = position angle. 

 1900. 



Dec. 7, i6h. 15m. Projection over Sinus Sabaeus; P. A. tang, to terminator 

 183O.2 

 22m. Projection continues (sketch). Height = % Th. 

 24m. P. A. terminator tang. 1 850.5. 

 26m. P.A. terminator tang. 1840.3. 

 30m. Projection continues; % y 2 to j^ Th. in height. 

 34^m. P.A. terminator tang. 182O.4. 

 37^m. Ht. I Th. ; no other irregularities on terminator. 

 39m. P.A. 182C.0. 

 41m. P.A. 184O.7. 



