GEOLOGY. 223 



tlioin. The antlior still liolds fast to his opinion tbat the celebrated 

 Calaveras skull, which Avas found by him beneath the lavas and jiravel 

 of the Pliocene formation, really was deposited with these gravels, and 

 is confident that he was not deceived. He is confirmed iu his opinion 

 by the ai)pearance of the skull and the testimony of others who have 

 examined it. On the other hand Uughes, Dawkins, and others are 

 convinced that all evidences of man's existence on the European conti- 

 nent before the x>iihTeolithic age are very unsatisfactory, and the age of 

 the Calaveras skull is a thing which even those who believe in its antiq- 

 uity will wait to see confirmed. 



The Ohio survey has, under the direction of Prof. J. S. Xewberry, pub- 

 lished a large volume and an atlas ; Alabama, New Jersey, Minnesota, 

 Indiana, Virginia, Kansas, and the Canadian geological surveys under 

 direction of their respective heads, have issued volumes and reports 

 which render knowledge concerning the structure and resources of these 

 areas accessible. 



There has been a considerable amount of work done in the mean time 

 l>y individuals. It is to be considered as probable that such work will 

 always take high rank in value, because it is undertaken only on account 

 of deep personal interest, and is more limited iu extent, and therefore 

 often more thorough. Much of the work referred to beyond is the 

 result of private enterprise. 



STEATIGRAPHY. 



The great mass of the communications to geological science from this 

 country have dealt with stratigraphical geology. The volumes of sur- 

 veys to which I have referred have been shown to be so ]umierous that 

 I can do no more than to simply indicate that there has been great ])ro- 

 gress in the development of detailed knowledge of the stratigraphical 

 arrangement all over the country. I may recall in this connection the 

 work of Professor Dana, by which the so-called Taconic system of schists 

 are shown to belong to the Hudson River i)eriod. The age of this sys- 

 tem of rocks, which is of much importance iu Green Mountain geology, 

 has been long a matter of dispute, and has been discussed by very many 

 able geologists, and this is not the first time that Professor Dana has 

 expressed his opinion upou this point. His studies have also led him to 

 think that the limestones of Westchester County and New York Island 

 and the associated metamorphic rocks are of lower Silurian age, as are 

 also the limestones and very likely the associated schists of the Green 

 Mountain region. These conclusions, if they are agreed in, must be of 

 very great importance, for at the present time it is generally considered 

 here and abroad that the presumption is in favor of the Archiean age 

 of a thoroughly crystalline schist. Note, for example, the German 

 nomenclature of the Archsean formation. Its lowest member is the 

 "Urgneiss" formation, and its next member is the " Krystallinische" 

 or the "Urschiefer" formation. The recognition of a whole system 



