128 REPOET OF THE 



remarkable feature seen here, however, is the occurrence of 

 two parallel grooves crossing the first set and bearing N. 60° 

 E. These grooves are 4 ft. 6| inches apart, If inches deep, 2 

 inches wide, and 25 feet long, issuing from under the cover of 

 diluvial materials, and terminating at the point to which the 

 waves have broken away tke rock. The first impression which 

 irresistibly forces itself upon the mind, is^the conviction that a 

 loaded wagon has been driven over the surface while in a yield- 

 ing condition; and a couple of grooves parallel to these, seen 

 for a part of the distance like the tracks of the second pair of 

 wheels, greatly confirms the illusion: 



The Island of Mackinac shows the most indubitable eviden- 

 ces of the former prevalence of the water, to the height of 250 

 feet above the present level of the lake; and there has been an 

 unbroken continuance of the same kind of aqueous action from 

 that time during the gradual subsidence of the waters to their 

 present condition. No break can be detected in the evidences 

 of this action from the present water-line upward for 30, 50 or 

 100 feet, and even up to "the level of the grottoes excavated in 

 the brecciated materials of "Sugar Loaf," the level of "Skull 

 Cave" and the " Devil's Kitchen." 



While we state the fact, however, of the continuity of the 

 action during all this period, it is not intended to allege that 

 the water of the lakes, as such, has* ever stood at the level of 

 the summit of Sugar Loaf. Nor do we speak upon the question 

 whether these changes have been caused by the subsidence of 

 the lakes, or the uplift of the island and adjacent promontories. 

 It is true that the facts presented bear upon these and other 

 interesting questions, but we must forego any discussion of 

 them.* 



♦Abundant evidences are furnished along the shores of Lake Huron, of the unbroken con- 

 tinuity of the action of those physical forces which have transported and assorted the mate- 

 rials of the Drift. From the shingle beach formed by the violence of the last gale, we 

 trace a series of beaches and terraces, gradually rising as we recede from the shore, and 

 becoming more and more covered with the lincbens and mould and forest growths which 

 denote antiquity, until, in some cases, the phenomena of shore action blend with the 

 features which characterize the glacial drift. These observations tally so well with the 

 views of Pictet on the continuity of the Diluvian and Modern Epochs, as established by 

 palaeontological evidences, that I cannot forbear referring the reader to an article of his 

 which falls under my notice as this report is going through the press. See JHbliotheqiu 

 Universale de Qmeve, Vol. VIII. , p. 265. AUo, SiUiman's Journal, [2] XXXI, 345. 



