I am grateful to Drs. R. R. Heinrich, D. E. Hudson, C. Kisslinger and W. Stauder and to Messrs. D. Leeds, R. Herrmann, A. Necioglu and J. Zollweg for useful suggestions. Dr. B. A. Bolt asked a critical question, which caused me to rethink the procedure for calculating the magnitude of the 1811 earthquake. Miss M. Bires and Mr. D. Shocklee were helpful in acquiring microfilm copies of the old newspapers. Mr. D. Leeds kindly provided a copy of Mitchill's paper, and Dr. T. S. Murty supplied the geographic coordinates of Fort William Henry. Dr. B. J. Mitchell made his manuscript available to me before publication.

The study was supported by grant GA-20115 of the National Science Foundation, Earth Sciences Section.