R. T. Hill—Cross Timbers in Northern Texas. 991 
well with the figures given above. The mineral is therefore a 
combination of bismuth carbonate and hydrate. Comparing 
this formula with BiC, which is given by Weisbach* for his 
bismutospheerite, or rather with its equivalent Bi,C,O,+2Bi,0,, 
we see that they differ only in the hydration of the bismuth 
oxide. If we regard the loss in Winkler’s analysis as water, 
and after deducting the silica found, calculate to one hundred 
per cent, it becomes Bi,O, 88°83, CO, 8°90 and H,O 2°18, 
also quite near the figures required by the formula. 
It is to be hoped that there will be a new examination of 
bismutospheerite, for it certainly is a suspicious circumstance 
that the loss in the analysis given, an analysis on which a new 
name is based, should be exactly the amount of water required 
to make it the well-known mineral bismutite. 
Clinton, N. Y., February 16, 1887. 
Art. XXXIV.—The Topography and Geology of the Cross Tim- 
bers and surrounding regions in Northern Texas ; by ROBERT 
T. Hinu.t With a Map, Plate VI. 
THE Cross Timbers of Texas are two long and narrow strips 
of forest region between the 96th and 99th meridians, ex- 
tending parallel to each other from the Indian Territory south- 
ward to the central portion of the State, forming a marked 
exception to the usual prairie features of that country. They 
have been delineated upon several maps, but most accurately 
upon the one accompanying the ‘‘ Report on the Cotton Produc- 
tion of the State of Texas, with a Discussion of the Agricul- 
tural Features of the State,” by R. H. Loughridge, Ph.D..,. 
Special Agent of the Tenth Census,{ which has been adopted 
in the map illustrating the areal distribution of the geologic 
formations of the United States, published in vol. v, of the 
Annual Reports of the Director of the U.S. Geological Survey. 
The traveler, in crossing this region of Texas from east to 
west, along the line of the Texas and Pacific railroad, views ~ 
the Cross Timbers merely as a grateful relief to the monotony 
of the prairies, and sees little in them worth remembering. 
To the more careful observer, however, there are numerous 
® points of interest bearing on their topographic and geologic 
relations, some of which are worthy of presentation. 
* Jahrb. Berg-Hiitt., 1877. ° 
+ Read before the Philosophical Society of Washington, Jan. 29, 1877. 
¢ Rep. Tenth Census, vol. v, pt. I, 1884, pp. 653-831. 
