EXCESSIVE RAINS 33 



inch, and 119 were less. Mr. Gray pointed out that great 

 care must be taken to determine the exact duration of the 

 storm, and also of the heavy showers that may fall during a 

 long rain, and that meteorological records are to be used only 

 with great caution. He explained that the records, as generally 

 made, can seldom be depended on for the rates of fall, since 

 as a rule they give only the total amount of rain falling at 

 certain times, paying little heed to the exact time when the 

 storms begin or end; that is, the records fail to distinguish 

 between a fall of i inch within the hour, however short the 

 actual duration of the storm, and another which continues 

 at a constant rate for the whole hour. Mr. Gray, however, 

 gave no precise data as to the proper amount to be considered 

 in the case of the Providence sewers. 



With the demand for more knowledge, aroused in great 

 part by the work of a few engineers, came more data from 

 different parts of the country to which the engineers of the 

 Boston Water Board contributed largely. It was soon found 

 that the early records were not entirely trustworthy, that the 

 location of the gage had not been well considered, and that 

 the rate of fall could not be derived with any exactness from 

 published records either public or private. 



In 1888 the U. S. Weather Bureau began reporting excessive 

 rains, i.e., rains of 2.50 inches or more in twenty-four hours 

 and of i inch or more in one hour, but from the nature of the 

 observations it is rarely known, in the case of rains of an inch 

 or more in an hour, whether the rain was of an even intensity 

 for the whole period, or whether most of it fell in a small 

 fraction of the time. These records, with such value as they 

 possess, are now available, as noted at the Weather Bureau 

 stations through the United States (see Monthly Weather 

 Review). 



By a study of these figures it is seen that rainfalls of the 

 rate of an inch per hour, assumed by Col. Adams and Mr. 

 Shedd to be rare, are by no means infrequent. It is now 

 proved that such storms occur several times a year, instead of 



