1820.] Specific G rumty of Gases. 177 



Professor Berzelius, Mr. Dalton, and indeed eveiy person who 

 has hitherto turned his attention to the atomic theory, are 

 obviously not susceptible of any ^reat degree of precision. They 

 have been guided entirely by the analytical researches without 

 any general principal to direct their choice. Hence the very 

 great diversity apparent in the numbers on which they have 

 pitched, and the complicated nature of the numbers themselves; 

 whereas it will be easy to show, when we have established the 

 true specific gravities of the gases, that the numbers denoting the 

 relative weights of the atoms of those elements that enter into 

 the constitution of the gases are of the most simple kind, and 

 that they are possessed of properties, which, if duly studied, would 

 soon lead us a great way into the knowledge of the constitution 

 of the vegetable and animal kingdoms. But I avoid entering 

 upon this subject till a future opportunity. 



{To be continued.) 



Article II. 



On Rain-Gaiiges. By Mr. H. Boase. (With a Plate.) 

 (To Dr. Thomson.) 



STR, Penzance, Juli/ \2, 1820. 



Your respectable correspondent Mr. Meikle {Annals of Philo- 

 sophy for April, p. 269), appears to me to have too hastily con- 

 cluded that " the quantily of water received by the rain-gauge is 

 totally independent of the general inclination of the rain." 



First, Because common experience proves that more rain falls 

 on a given surface in equal time during a calm than during a 

 storm, other circumstances being the same. To this every 

 superintendant of a rain-guage, or gardener, or agriculturist, will 

 bear uniform testimony. 



Second, Because the principle of the parallelogram adopted by 

 Mr. Meikle in this case proves too much ; for if " the perpendi- 

 cular distance of the drops of rain varies icith the sine of inclina- 

 tion, while it is the distance of the points in tchich the drops pass 

 through a horizontal plane that is invariable" then a greater 

 ijuantity of water will be received by the rain-guage (other 

 circumstances being equal) in proportion to the sine of inclination ; 

 for (adopting Mr. Meikle'.s own diagram) let A B (PI. CVII.) 

 fig. 1, the vertical column of rain, be inchned to an angle 

 ot 30° as A D, the perpendicular distance of the drops will 

 be reduced one half, consequently the whole assumed column 

 A B will be received within the ellipsis c e d f. Suppose the 

 diameter of the basin uC b d (or a d b c) divided into 10 parts 

 (inches, miles, or leagues), the area of its surface wil l be 10- x 

 •7854 = 78-5400; hence the ellipsis c e df must be 10 x 3 x 



Vol. XVI. :)i° III. M 



