250 RECORD OF SCIENCE FOR 1887 AND 1888. 



and nothing" remains to indicate their existence save the indurated con. 

 tents of the pipes by which they were supplied. These remnants of 

 lava cohimns, or "volcanic necks" as they are called by Button (by 

 whom they were discovered and interpreted), are among the most inter- 

 esting records of vulcanism extant, since by means of them the geologist 

 descends far into the crust of the earth toward the ultimate seat of vol- 

 canic action. 



In the early days of geology there were two rival hypotheses concern- 

 ing the formation of the rocks of the earth, viz, the Plutonic and the 

 Neptunic. The battle between these doctrines raged for a generation 

 before theNeptuuists gained the ascendancy; but it is now recognized 

 that by far the greater part of the rocks open to observation were de- 

 posited in the seas, and that only a subordinate part were extruded in 

 molten condition from the bowels of the earth. Yet a vestige of the 

 Plutonic hypothesis has persisted until to-day, particularly in Germany, 

 but to some extent in this country, in the form of a belief that the vol- 

 canic rocks of the earth represent a more or less definite series ranging 

 and gradually changing from the Archean to the Pliocene — that the la- 

 vas of the Paleozoic were unlike those of the Mesozoic, and these again 

 unlike those of the Ceuozoic, and that the successive differences consti- 

 tute a record of the earth's history, susceptible of an interpretation only 

 less defiinite than that afibrded by the succession of organic life. This 

 belief (which must not be confounded with Eichthofen's induction con- 

 cerning the succession of rocks among the lavas of a particular province 

 and period, and Button's admirable explanation of the law of that succes- 

 sion) was so seriously shaken when the results of the investigation of the 

 Washoe rocks of Nevada by Hague and Iddings were published* that 

 it has now been largely abandoned by German students and teachers. 

 So an American discovery has, within the biennial period, and in at 

 least one foreign country, practically revolutionized thought concern- 

 ing the snccession and significance of volcanic rocks as geologic chro- 

 nometers. 



Although sometimes unquestionably connected with general deforma- 

 tion, seismism or earthquake movement is known to accomi)any vol- 

 canic action in many cases. Buring the biennial period the most im- 

 portant contribution ever made to seismology — a contribution which 

 revolutionized earlier conceptions and placed the entire science ui)on a 

 new and firm foundation- — enmnated from the American geologist But- 

 ton, as the outcome of his studies of the Charleston earthquake of ISSG. 

 The contribution includes two distinct conceptions: (1) It was found 

 on examining the means hitherto em])loyed for ascertaining the depth 

 of earth(iuake foci that, all involve sources of error of such magnitude 

 that the resulting determinations are worthless; and so a method was 



» Bull. U. S. Geol. Survey, No. 23, 1886. 



