C. Barus — Viscosity of Gases at high temperatures. 407 



trusive belt. At several points both east and west there 

 are fragments of moraines of undoubted character. These 

 outer occurrences are significant, but their full meaning will 

 only be understood when detailed work shall have shown 

 their relationships. It is not impossible that a chain of 

 such isolated formations may be found to be so situated 

 with reference to each other, as to indicate an outer mo- 

 raine of greater age than the northern group. It is possible 

 that some of the accumulations there included, belong rather 

 with these outer fragments, in time of origin, though not 

 widely separated geographically from the later formations to 

 the north. In this case, the variation in the position of the 

 ice-front at different epochs must have been great. 



The failure to bring the drift formations of the continent of 

 Europe into closer correspondence with those of our own 

 country, is "to be attributed, in part at least, to the absence of a 

 common basis of study. The terminal moraines are unques- 

 tionably the most conspicuous, and by means of their topog- 

 raphy the most easily recognized of the drift formations. 

 They are therefore especially adapted to serve as common 

 centers of study, and with this one common phase of the drift 

 formations, which may be in some sense a standard of compari- 

 son the work of geologists on opposite sides of the water 

 may, more readily than heretofore be correlated, and such cor- 

 relation cannot fail to facilitate the solution of the many yet 

 unsolved problems in glacial geology. 



Heidelberg, Nov. 15, 1887. 



Art. XXXY. — Note on the Viscosity of Gases at High Tem- 

 peratures and on the Pyrometric use of the principle of 

 Viscosity ; by Carl Barus.* 



By passing gases under known conditions through capillary 

 tubes of platinum, kept at measured temperatures between 

 5° and 1400°, I have found a series of data for the relation be- 



* The forthcoming Bulletin of the U. S. Geological Survey to which the present 

 note refers, is a first contribution to 'a research on the physical constants of rocks, 

 the experiments of which are to follow a general plan devised by Mr. Clarence 

 King. The Bulletin in question is restricted to methods of high temperature 

 measurement and will be in six parts, of which the first is a brief historical intro- 

 duction. Chapter I of the work discusses experiments which Dr. William Hal- 

 lock and I made in New Haven with a very large high temperature apparatus. 

 In Chapter II (which with the following chapters is my contribution) I investigate 

 apparatus and methods for the practical calibration of electrical pyrometers by aid 

 of fixed thermal data ? In Chapter HI I discuss certain pyrometric qualities of 

 the alloys of platinum generically, and tho data lead to curious electrical results. 

 In Chapter IV I describe methods for the calibration of electrical pyrometers 



