C. D. Walcott — Position of the Olenellus Fauna. 29 



If we adopt the value of wi=0*652 and value of «=l - 0088 

 in (29), which have been shown to be probably more nearly 

 correct values for low temperatures, we get t= — 19°. With 

 a larger value of the solar constant these temperatures denoted 

 by r would be higher. 



By means of (6) we get from (37) 



(39) m— — =1— A 



v ; 273* 4 ar 



The most probable values of m and e for low temperatures are 

 that of §20, m=0438, for the former, and that of equation 

 (23) for the latter, though the value of m here deduced from 

 the radiation of glass at high temperatures should be increased 

 a little for a lampblack surface. With these values (39) gives 

 T = 291° or r=18°, which is a little above the mean tempera- 

 ture of the earth's surface. The values of m deduced from 

 experiments at high temperatures, by D along and Petit's law 

 and the values by Stefan's law are found to differ very much, 

 the former being the greater, and the same is true with regard 

 to any modification of these laws, by giving different values to 

 the constants a and e in the general expressions of (1) and (6), 

 but in deducing the values of a and e from experiments at 

 lower temperatures we find that the corresponding values of 

 m decrease in the former case and increase in the latter, so that 

 the tendency is to bring them nearer together. The true 

 value, no doubt, lies somewhere between, but to determine it 

 with greater accuracy it is important to have experiments upon 

 radiation at much lower temperatures than those of any experi- 

 ments yet made. 



Art. III. — Stratigrayhic Position of the Olenellus Fauna 

 in North America and Europe • by Chables D. Walcott, 

 of the IT. S. Geological Survey. 



(Continued from page 392,' vol. xxxvii.) 



Since the first part of this article was written the review of 

 all the species known to me from the Lower Cambrian or 

 Olenellus zone in North America has been completed. To 

 the list published {ante, pp. 388, 389) there are to be added 

 the genera JSTothozoe, Modioloides and Straparollina, and the 

 species Lingulella, sp. undet., Camerella minor, n. sp.,Pamelli- 

 hranch, gen. and sp. ? (Shaler and Foerste), Scenella, sp. undet., 

 Straparollina remota Billings, Nothozoe ? Vermontana and 

 Olenoides quadriceps H. & W. Paradoxides f Walcotti is 

 referred to Olenellus and Modiolopsis {??) prisca to Modio- 



