abstracts: geology 403 



but was done a little at a time, in order to interfere as little as possible 

 with the observations. The observing was completed in four summer 

 seasons, beginning in June, 1903, and ending in July, 1906. 



The length of the primary triangulation of this arc, along the axis of 

 the scheme, is 577 miles (929 kilometers) and the length of the subsidi- 

 ary schemes, secondary in character, is about 30 miles (48 kilometers). 

 Fifty-seven stations constitute the main scheme. The mean latitude of 

 the three old stations of the Thirty-ninth Parallel triangulation, from 

 which the arc started, is 39° 05', and the northernmost point lies in 

 latitude 47° 23'. The triangulation follows closely the meridian of 

 122° 30'. 



There were used to control the lengths in this triangulation the Yolo 

 base in California, the Willamette base, near Eugene, Oregon, and the 

 Tacoma base, near Tacoma, Washington. The Yolo base was meas- 

 ured in 1881 in connection with the transcontinental triangulation, 

 while the other two bases were measured in 1906. 



Each of the triangulation stations was well marked and hence is 

 available for the surveyor and engineer. The publication contains de- 

 scriptions of the location and marking of the stations, also the latitude 

 and longitude of each point in the scheme and the azimuth of each line 

 observed over for horizontal directions. 



A series of sketches and an index enable one to find readily the data 

 for any portion of the area covered by the triangulation. W. Bowie. 



* 



GEOLOGY. — The Onondaga fauna of the Allegheny region. E. M. 

 Kindle. U. S. Geological Survey Bulletin 508. Pp. 144, with a 

 map and sections. 

 , The Onondaga limestone is represented from Hudson River to Lake 

 Erie by a zone of frequently recurring outcrops across central New York 

 State. Passing under Lake Erie, the fauna reappears in rocks of the 

 same lithologic facies in northern and central Ohio, and reaches as far 

 west as Louisville. The most westerly recorded appearance of the fauna 

 is at the Bake Oven, in southwestern Illinois, so that it has an east- 

 west extension of about 1000 miles. In sharp contrast with this con- 

 siderable westerly extension of the Onondaga fauna beyond its type 

 region in eastern New York is the comparatively insignificant southerly 

 extension of the fauna and formation as it has been generally recognized. 

 The formation barely crosses Delaware River, according to most of the 

 papers dealing with the stratigraphy of the Devonian in the Allegheny 

 region, which give it a north-south extension of scarcely 200 miles. This 



