228 ROCHESTER ACADEMY OF SCIENCE. [April 14, 



ern New York along the lower St. Lawrence and sometimes at 

 Buffalo, and always o\er the upper lakes, particularly south of Lake 

 Superior. To return to rainfall, including snowfall melted as a part 

 part thereof, an examination of the records shows that the greatest 

 average rainfall occurs during the ten days ending June 28th, during 

 which 1.23 inches is the normal. The ten days ending June 8th is a 

 close second, with 1.22, and also January 14th, with 1.21. The least 

 rainfall occurs with 0.63 during the ten days ending August ytli, with 

 0.73 during the ten days ending February 4th as a close second. 



The greatest rainfall for any ten days is 6.40 ending October 26th, 

 1873, and there have been eight instances of ten days passing without 

 any fall whatever during the last 25 years. By 30-day periods the 

 greatest average is the 30 days ending June 8th, in which 3.39 inches 

 falls, and the least during the 30 days ending October i6th, in which 

 the average is 2.35, showing a range in 30-day averages of only 1,04 

 inches. 



The greatest rainfall for 30 days was in the 30 days ending Novem- 

 ber 15th, 1873, 9.20 inches; the least, 0.20, November 15th, 1874. 

 In percentage of days on which o.oi or more precipitation occurs, the 

 normal daily record varies from 67, January i8th, to 33, September ist. 

 The greatest 30-day record is 90 per cent., February 3, 1874, and the 

 least 7 per cent., September 6, 1876. As to the distribution of rain- 

 fall through the year, 24 per cent, of the annual rainfall comes to 

 Rochester during the spring, 26 per cent, during the summer, 24 per 

 cent, during the autumn and 26 per cent, during the winter. At 

 Boston the same record is 24, 24, 25, 27 ; New York, 24, 28, 24, 24 ; 

 Buffalo, 21, 26, 28, 25 ; Chicago, 26, 30, 25, 10 ; Omaha, 28, 43, 

 26, 6 ; Los Angeles, 21, 2, 13, 64 ; San Francisco, 25, o, 17, 58 ; 

 Portland, 24, 6, 24, 46 ; St. Vincent, 20, 45, 23, 12. Rochester 

 shows a variation of only 2 per cent, for the seasons, against 3 at 

 Boston, 4 at New York, 7 at Buffalo, 1 1 at Chicago, 37 at Omaha, 

 62 at Los Angeles, 58 at San Francisco, 40 at Portland and 33 at 

 St. Vincent. 



An interesting point in this connection is the average rainfall for 

 the entire United States. The average of all stations by states gives 

 for spring about 9 inches, Rochester has 9 ; summer, 10, Rochester, 

 9 ; autumn, 8, Rochester, 8 ; winter, 9, Rochester 9 ; total yearly, 36 

 inches ; Rochester, 34. It appears that the rainfall over the United 

 .States generally is (juite evenly distributed through the year, varying 

 in total amount for the seasons from 10 inches for summer to 8 inches 

 for autumn. The variation at Rochester is even less than this, being 



