The following paper is a resume of a series of sun-spot observations commenced by the writer in 1890, August 1st, and continued without interruption, except by cloudy weather and other unavoidable causes —such as sickness or absence from the city— until the present time.
Proceedings of the Iowa Academy of Sciences
©1902 Iowa Academy of Science, Inc.
Hadden, David E.
"The Solar Surface During the Past Twelve Years - A Review of Sun-Spot Observations Made at Alta, Iowa, from 1890 to 1902,"
Proceedings of the Iowa Academy of Science, 10(1), 74-98.
Available at: https://scholarworks.uni.edu/pias/vol10/iss1/14