HO HYDRAULIC INVESTIGATION*. 



In the six experiments which Dubuat has wholly rejected, 

 the mean errour of his formula is about t 't> an ^ tnat of 

 mine T V» In fifteen of Ger.-tner's experiments, the mean 

 errour of Dubuat's rule is one third, that of mine one 

 fourth ; and in the three experiments which I made with 

 very fine tubes, the errour of my own rules is one fifteenth 

 vf the whole, while in such cases Dubuat's formulae com- 

 pletely fail. I have determined the mean errour by adding 

 together the logarithmic ratios of all the results, and divid- 

 ing the sum by the number of experiments. It would be 

 useless to seek for a much greater degree of accuracy, un- 

 less it were probable, that the errours of the experiments 

 themselves were less than those of the calculations; but if 

 a -sufficient number of extremely accurate and frequently 

 repeated experiments could be obtained, it would be very 

 possible, to adapt my formula still more correctly to their 

 results. 

 i In order to facilitate the computation, I have made a ta- 



ble of the coefficients a and c for the different values of d, 

 all the measures being still expressed in French inches. 



Table of Coefficients for French Inches. 



For 



