20 Barus and Strouhal— Viscosity of Steel. 
traversed by the Rio Sabinas, a tributary of the Rio Grande. 
I traced the Laramie strata along the north side of the Sabinas 
valley for a distance of nearly forty miles, beginning a few 
miles above Sabinas station of the Mexican and International 
Railroad, and going down the valley to the southeastward. At 
the hamlet of San Felipe, about fifteen miles below Sabinas 
station, some important mines have been opened in the Laramie 
Group on both sides of Rio Sabinas; and the presence of coal 
in the same formation has been proved at several other locali- 
ties in the same district. 
On the south side of the river, some twenty miles southwest- 
ward from Sabinas station, and westward from the railroad, 
exposures of coal were observed in strata equivalent with the 
Fox Hills Group, but no important mines have yet been 
opened there. 
Little is yet known of the character of the coal deposits in 
the southern part of Presidio and El Paso counties, Texas, re- 
spectively; but the coal which is found at White Oaks in 
Southeastern New Mexico, some 75 miles northeastward from 
Kl Paso, is reported to be of good quality. Coal of either 
Laramie or Fox Hills age, or both, is also well known to exist 
at many localities in New Mexico and Colorado, along the 
eastern base of the mountains. It will thus be seen that there 
is a belt of these two coal-bearing formations extending nearly 
or quite continuously from the valley of the South Platte in 
Colorado to the State of Nuevo Leon in Mexico. 
It is not necessary to inform the practical geologist that this 
series of strata is entirely distinct from the coal-bearing rocks of 
Carboniferous age which extend southward through the Indian 
Territory into Northern Texas, and also distinct from the 
Tertiary lignite beds which range through eastern Texas and 
portions of other Gulf States. 
Art. WI.—The Viscosity of Steel and us Relations to Temper; 
by C. Barus and V. STROUHAL. 
[Continued from vol. xxxii, page 466. | 
Miscellaneous experiments.—1. In tables 27 and 28 we cite 
the results obtained when one of the steel rods is replaced by a 
fiber of glass. The mean thickness or the diameter 20, of 
glass was intended to be that of the steel rod 20,; but it is 
smaller in table 27 and considerably larger in table 28. It is 
impossible to store a greater total torsion than ¢,—(—¢,)=90° 
in the given system without breaking the glass fiber. The 
equality of ¢, and ¢, is assumed merely for convenience in des- 
