June 9, 1916] 



SCIENCE 



825 



focus will be refracted towards the other and 

 the two points E and E' are therefore conju- 

 gate foci, and / and /' may be substituted for 

 OE and OE'. 



A very similar solution which need not be 

 given here can be obtained for the cases where 

 one focus lies between Q and F or F' and the 

 other on QE or QE' produced and which result 

 in virtual instead of real images. 



This equation applies to the refraction at 

 one lens surface. For simple lenses or for 

 lens systems two or more equations, according 

 to the number of refractions, must be com- 

 bined. 



When the cone of light is narrow and does 

 not diverge far from the optical axis the last 

 factor cos a/cos h becomes practically 1. This 

 produces the simplest form of the equation. 

 It can be used in calculating the foci of thick 

 lenses in case the aberrations are neglected. 



For the study of aberration the angles a and 

 b can be calculated by solving the two triangles 

 EDO and QDO in which EO and QO remain 

 constant and the other sides vary according to 

 the refractive index of the color of the ray 

 of light investigated in the study of the 

 chromatic aberration, or according to the posi- 

 tion of Q when studying spherical aberration. 



The usual equation found in the books can 

 not be employed for either of the foregoing 

 calculations when more than approximate re- 

 sults are required. C. W. WoODWORTH 



ANTHROPOLOGY AT THE WASHING- 

 TON MEETING 



II 

 A New Type of Euin Beoently Excavated in the 



Mesa Verde National Parle, Colorado : J. Walter 



Fewkes. 



An account of the excavation and repair of a 

 new type of ruin on the point of a mesa opposite 

 Cliff Palace, conducted under the auspices of the 

 Interior Department and the Bureau of American 

 Ethnology. Before the work was begun, the exist- 

 ence of a large building was indicated by a large 

 mound, the surface of which was strewn with 

 artificially fashioned stones, partly covered with 

 soil, with a few feet of wall showing at one point. 

 On top of the mound, at a place found later to 

 indicate the highest wall, grew a large cedar tree. 



a cross-section of which revealed 360 annual rings. 

 The building excavated is D-shaped, measuring 122 

 feet on the straight side and 64 feet broad. The 

 standing walls now contain 120,000 cubic feet. 

 The facing of the walls is artificially pecked with 

 stone implements, and in many instances rubbed 

 smooth. Many stones set in the walls or found in 

 the debris bear incised ornamentation, the begin- 

 ning of mural embellishment. The masonry is not 

 only among the best in any prehistoric building 

 north of Mexico, but the building itself is the 

 most mysterious yet brought to light in our south- 

 west. 



There are evidences that it was neither com- 

 pleted nor inhabited, and evidently it was not in- 

 tended for habitation. Its ground-plan exhibits a 

 unity in design and a strict adherence to that plan 

 throughout the construction of the building. It 

 is believed to have been constructed by the neigh- 

 boring cliff-dwellers; it is prehistoric and regarded 

 as more modern than Cliff Palace. A fossil leaf 

 of a palm in relief on the upper surface of the 

 cornerstone at the western end of the building is 

 believed to be a sun symbol, and the walls about 

 it a solar shrine. The building is regarded as a 

 sun temple of the neighboring cliff-dwellers, and 

 is the first of its type yet excavated in the Mesa 

 Verde National Park. 

 The Passing of the Indian: James Moonet. 



The subject of the aboriginal population of 

 America, and more particularly of the United 

 States, at the first coming of the white man, has 

 been a matter of much speculation, but of very 

 little detailed investigation. There has been about 

 as much error and loose statement on one side as 

 on the other, some theorists claiming for the pre- 

 Columbian period a dense population for which 

 there is no evidence in fact; while others, largely 

 those interested in various civilizing schemes, 

 maintain that the Indian has held his own or is 

 even actually increasing. The claim for a dense 

 earlier population is based chiefly on ignorance of 

 Indian living habit and the error of assuming as 

 contemporaneous in occupancy settlement remains 

 belonging to widely separated periods. The argu- 

 ment for stability or increase of the Indian popu- 

 lation rests in part on the error of beginning the 

 calculation with the beginning of federal relations 

 with the tribes, ignoring the centuries of coloniza- 

 tion and disturbance which preceded that period, 

 and is also colored to some extent by a desire to 

 draw good results from philanthropic and civilizing 

 efforts. 



