52 PROCEEDINGS OP THE AMERICAN ACADEMY 



bringing all the data together in a convenient shape for further exami> 

 nation. The errors of the method consist in the assumption of uni- 

 form shape of the storm-front, and a uniform velocity of progression; 

 but I do not think they are serious in this case. The convexity of ^he 

 storm-front is perhaps too great, but that it was really well bowed 

 forward is shown by the late arrival of the rain at the lateral, as com- 

 pared with the central stations. The concavity of the rear of the 

 rain area is not so well established, but it seems to have approached 

 a parallelism to the front. 



83' 



^Z' -80-' "~-.^86'/a" ,^0' "-vSr 



- -^-H ''- - .\-7 -"^--V-4 



NO »- ^ ^-*| ' 



y 



-- X ..>..\.6 _-- ■^-z .--... ^.\a.~.- ...^.Vl- 



\ -s- - *- - -V<i ■ • r ■ - - --«'< • • •"'Sacr-.- -\'' - 



'. * » * ' . 

 ;-a ..,-s ^„ ,...,. ..^o --V, 



t /:^:::;-.\;^^^r^ ■^^-^.-- ^^^^-^-i^-^s c-.-:^::^? 



/ ' ''- ^ ♦ / / 





/ 



,.i, . y.,3 ,.. -A — y^,s _ . . ^ ^f/7 ..-.-..-.-. -.,-^o .J:vr.-.;^o°. ■-- 



„^^ --ji-- 7-^-16 -is---i^^-t -^o .,•'♦( — :_ 



--->'-6 .....^<J .„ ^- #-*- 1-— ». --^o — z,'*}^-" 





Fig. 7. 



The changes of temperature with the passage of the storm are well 

 determined. For their better illustration I have prepared Fig. 7, as 

 follows : by interpolation, an approximate temperature was determined 

 for a number of stations at the several fifteen-minute lines of Fig. 6 ; 

 then, taking the temperatures at fifteen ramutes before the rain as 

 standards, the departure from them was determined for the other 

 times, and these plus and minus numbers are exhibited in Fig. 7. 

 Averaging the departures and the observed temperatures on every 

 time line gives the following results : — 



