240 On the Polished Limestone of Rochester. 



once more thank you in all earnestness and sincerity for your 

 good opinion which placed me in this chair, and for the kindness 

 and support which I have on all occasions received from you ; 

 and with by best wishes for your prosperity, and that of your 

 science, I resign my office into abler hands. 



Art. IV.— On the Polished Limestone of Rochester ; by Prof. 

 Chester Dewey. 



TO THE EDITORS. 



Only a partial notice has been given of this limestone, found in 

 and about this city. The upper surface of the transition limestone 

 through which the Genesee river here passes, is in many places 

 found polished at various depths under the diluvial deposit and 

 soil. A small surface of 7iatural polish might pass unregarded j 

 but a surface of many acres, and over a space miles in length and 

 breadth, is no ordinary fact, and one not admitting of the most 

 ready explanation. The fact' has been merely mentioned in 

 the geological reports of this State. Beginning three miles west 

 of the Genesee in the town of Gates, the railroad is cut through 

 the polished limestone for more than a hundred rods in width ; 

 the stone being covered with earth from two to eight feet deep. 

 The polished layer is commonly at this place three or four inches 

 thick, bituminous strongly, rather brittle, breaking into irregular 

 fragments. The polish is often so fine as to show faintly, objects 

 by reflection of the light. It would be a beautiful article for win- 

 dow sills, if it could be obtained readily of the proper dimensions, 

 as it is already smoothed for this use. Half a mile north, the pol- 

 ished rock Avas struck in digging a well, and half a mile east of 

 this in digging a cellar, and half a mile farther east in digging a 

 well, and afforded beautiful specimens ; this was seven feet below 

 the surface. More than a mile farther east, about half a mile 

 west of the Genesee, it was struck at the depot of the railroad, 

 nineteen feet below the surface. Half a mile south of this, the 

 Genesee valley canal is dug through this rock for thirty rods ; 

 the upper layer being a foot or more thick, and four or five feet 

 under ground. Though the polished surface ceases at each ex- 



