MICHIGAN ACADEMY OF SCIENCE. 
87 
than its average then. So the Sault had quite different values when 
reduced for epoch with reference to these two stations respectively, 
32.5 inches by Marquette and 35.65 inches by Alpena. The distances 
are to Marquette 144 miles, to Alpena eighty-two. The list has been 
looked over for other similar cases. No differences so great were found. 
The fact is Marquette and Alpena are in regions contrasted in rain con¬ 
ditions. It is not possible to say beforehand to which group the Sault 
really belongs, though after trying both ways preference has been 
given to Alpena. Although the difference amounted to only three inches 
Fig. 5.—Rainfall chart with incomplete series of observations reduced by six groups of reduction 
stations. Shades 40, 35 and 30 inches. 
even in this case it was thought prudent to eliminate local influences 
that might be peculiar by a new reduction of all the broken series of 
observations with reference to the means of six groups of selected 
stations. 
1. Marquette, Parry Sound, Manitowoc, Alpena, Saugeen. 
2. Duluth, Marquette, La Crosse, Manitowoc. 
3. Port Huron, Lansing, Detroit, Wauseon, Chicago. 
4. Milwaukee, Chicago, Dubuque. 
5. Saugeen, Tort Huron, Toronto. 
6. Erie, Cleveland, Pittsburg. 
Fig. 5 shows the result of this reduction in map form. It only 
serves to confirm our faith in a reduction by single near stations as 
used for Fig. 1. No essential of Fig. 1 is changed, but the response 
