September 27, 1907] 



SCIENCE 



407 



to write this review for Science was, there- 

 fore, probahly due to this qualification as most 

 likely to produce an unbiased summary of the 

 book. 



With this explanation, he will proceed to 

 point out what seem to be the strongest points 

 and best features of this Volume III. of the 

 Annals of the Lowell ' Ohservatory, besides 

 those already mentioned above. 



Results secured at the opposition of 1894: 

 At Flagstaff 116 new canals were discovered, 

 44 in the dark regions and 72 in the light: 

 reobservation was made of 67 out of 79 of 

 Schiaparelli's earlier discoveries, which verified 

 the fixity both of existence and of position 

 {though not the continuous visibility) of the 

 canals: seasonal changes were disclosed by ob- 

 served changes in the markings : new knots at 

 intersections of canals were discovered, in the 

 ■dark regions as well as in the light, thus inci- 

 dentally exploding the supposition that they 

 are seas, but giving them rather the character 

 of oases : discovery of the so-called carets, 

 where the canals debouched. 



Ever bearing in his mind the degree of in- 

 credibility attached to these announcements by 

 most astronomers, the author points out that 

 the times of nearest approach of Mars through 

 the epoch most usual for observing may not be 

 always the most propitious season for multi- 

 plicity of detail. He also expresses the 

 opinion that the failure of others to see the 

 ■canals may be due to their looking at a 

 "featureless face" (page 7). On page 4, he 

 also points out a wide distinction between 

 " sensitive eyes " and " acute eyes " and shows 

 that a high ability to detect faint stars or 

 satellites may be the very criterion which 

 would presumptively preclude its possessor 

 from the securing of a retinal impression of 

 such surface features as Martian canals, etc. 

 This opposition was observed with an eighteen- 

 inch Brashear objective, usually with a power 

 of 320. 



At the opposition of 1896, a Clark objective 

 of twenty-four inches was used. At first, for 

 about three months at ITlagstaff, and after- 

 wards at Taeubaya, Mexico, the powers used 

 ranged from 163 to 528. Three hundred and 

 forty-one drawings of the complete disk were 



made at this opposition. As results, the enu- 

 meration includes many double canals — some 

 being always double, others only at certain 

 seasons of the Martian year. Evidence of the 

 canals in the dark regions as well as in the 

 light; and the subjective discovery that the 

 detail of canals and oases came out finer and 

 more minute as experience grew; and that 

 many apparent changes in appearances arose 

 " not because of change in them, but because 

 of growing aptitude in the observer." 



At the opposition of 1900, some canals were 

 seen still always double : and that, too, inde- 

 pendently of the apertures of the telescope 

 objective or of the optical interference bands. 

 Discovery was also made of bright spots in 

 various parts of the planet, and at times dif- 

 ficult to explain. Though seemingly fixed in 

 location, they were subsequently regarded as 

 Martian clouds. 



The opposition of 1903 was observed con- 

 tinuously for seven months while the tilt of 

 the planet's north pole towards us was nearly 

 at its greatest possible angle. The main re- 

 sults were noting the connection between the 

 oases and the double canals, the oases being 

 exactly embraced by the two arms of the 

 double, and the oases were round and the 

 canals tangent at the extremities of a diame- 

 ter. Also the observer noted an apparent con- 

 tradiction of Schiaparelli's announcement in 

 1888 of a change of longitude of Lucus Ismen- 

 ius. Changes of color were noted, and a semi- 

 annual fiux in the development of canals, 

 together with a complete confirmation of the 

 objectivity of the canal gemination, and much 

 additional information was gained as to the 

 nature of that gemination. 



In the Supplement, page 53, the author calls 

 particular attention to Mr. Douglass's remark- 

 able set of observations on the " projection " 

 of December 7-8, 1900, and affirms that his 

 observations and drawings showed conclusively 

 that the successive appearances could be ex- 

 plained only by clouds, and were perfectly 

 satisfied by that explanation. 



Herman S. Davis 

 DovEB, Delaware 



