THE MINERAL SPRINGS OF SARATOGA 6l 



We are not definitely assured as to the reaction which produces 

 the gas deep within the earth. Whether it is emitted directly from 

 cooling masses of igneous rock, as is not unreasonable from some 

 things that we know about them, or whether it results from the 

 action of the igneous rock on limestone, perhaps through the inter- 

 mediation of silicic acid, as was explained in an earlier paragraph, 

 may be a matter of uncertainty. 



If we endeavor to apply these views to the specific case of Sara- 

 toga, we are reminded of the volcanic plug discovered at North- 

 umberland, on the west bank of the Hudson, about ten miles a 

 little north of west from the springs in the village.^ The plug is 

 so isolated from all others of its kind and positive evidence of its 

 age is so difficult to obtain, that its time of outbreak is very obscure. 

 Since first studied ten years ago by Professors Woodworth and 

 Gushing, it has been nearly half quarried away for macadam and 

 concrete and its structure and features are much better exposed. 

 If anything they have made it more difficult to understand. The 

 complexity of the stratigraphical relations of the vicinity has been 

 increased by Doctor Ruedemann's discovery of late Cambrian fos- 

 sils in the slates. These matters will be fully discussed by Professor 

 Gushing in the Bulletin on the Saratoga Quadrangle. The writer 

 has had the privilege of visiting the plug with Professor Gushing 

 and Doctor Ruedemann and of discussing the question at length. 

 That the mass is volcanic seems to me the best explanation, and 

 that it is an elliptical agglomerate representing an old vent and 

 formed of bombs and masses of limestone torn off from the walls 

 of the throat down below, I feel convinced. The excessive altera- 

 tion argues for an outbreak which probably antedates the Tertiary 

 period, but to what extent I can not say. The plug is so far as 

 known the only purely volcanic rock within the confines of New 

 York, \'ermont, or of Massachusetts west of the Connecticut 

 valley. 



1 The plug was first recognized by J. B. Woodworth in the summer of 

 1901. It was carefully studied by him and described in the 21st Report of the 

 N. Y. State Geologist, p. r 17-r 24. The petrography was contributed by 

 H. P. Gushing, p. r 24-r 29. Professor Woodworth remarks the similarity 

 with the Triassic traps of the Connecticut valley; and Professor Gushing 

 very cautiously suggests the parallels between the plug and the same occur- 

 rences and those of the lower Hudson (i. e. the Palisades) and New Jersey. 

 A Triassic age seemed the best suggestion for a confessedly obscure and 

 uncertain occurrence. 



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