250 TRANSACTIONS OF THE [May 18, 
leozoic rocks. During a portion of the past three summers the 
writer has been at work in Clinton county, and has completed a 
preliminary survey of the county and studied some parts in great 
detail. During the progress of the work 102 dikes have been 
mapped, and these can constitute but a small proportion of those 
which really exist. In addition to these, 12 dikes have been 
described from the county by Kemp*, and two by Eakley, 
which the writer has not seen, making a total of 116 dikes known 
in the county. Out of this large number only five cut the Pa- 
leozoic rocks, yet these latter form the surface rocks over more 
than half the county ,and moreover the half in which the expo- 
sures are easily accessible and in which the detaiied work has 
been done. It should be noted that this discrepancy is by no 
means as marked in Essex county, just to the south, for more 
dikes are recorded there cutting the Palewozic series and the pro- 
portionate amount of territory underlaid by that series is vastly 
less. 
Distribution.—When the dikes are studied and classified 
another fact is brought out. Of the 116 dikes known in Clinton 
county, 11 are bostonites, 2 camptonites, 3 monchiquites, and the 
remaining 100 are diabases, though these latter vary toward the 
camptonites and monchiquites, and some of them show abnormal 
features. The diabase dikes far-outnumber all the rest, and are 
confined to the Pre-Cambrian rocks. A tabulation of the dikes 
described by Kemp from Essex county, and from the Vermont 
shore of Lake Champlain, brings out the same features.{ 58 
dikes are noted from Essex county, of which 48 are diabases, all 
of which cut the Pre-Cambrian rocks. 45 dikes are recorded 
from the Vermont shore,all in Palzeozie rocks, and of these but 
one has been recorded as being of diabase.§ This latter is of es- 
pecial interest as being the only recorded instance in the district 
of a dike of well-marked diabase cutting rocks more recent than 
the gabbo. The bostonites are found cutting everything from the 
gneiss of series I. to the Utica slate at the summit of series V. 
The distribution of the more basic dikes is puzzling. Of the 
non-feldspathic fourchite-monchiquite series but a single dike is 
known in the Pre-Cambrian rocks, viz., the dike of fourchite 
found by Kemp in the gabbro of Bouquet mountain, Essex 
county. But the total number of these dikes known from the 
New York side of the lake is not large, ail those described by 
Kemp, with the exception above noted, being found in Vermont. 
*J.F. Kemp. Bull. 107. U. S. Geol. Surv. 
+A. 8S. Eakle. Am. Geol.. July, 1893. pp. 31-36. 
* +{Bull. 107. U.S. Geol. Sury., pp. 54-59. Those described since the appearance of 
the pene merely increase the number of diabase dikes. 
2 Bull. 107. U.S. Geol. Surv. p. 48. 
