RESISTANCE. 



Since the above experiments of Mr. Robins, Dr. Hutton 

 has profecuted the fubjeft to a much greater length. His 

 experiments were made not only with the whirling machine 

 invented by the former, but with cannon balls of different 

 weights, from lib. to 61bs. ; as alfo with figures of various 

 fhapes, and with planes fet at a variety of angles of inclina- 



tions to the path of motion. From thefe experiments the 

 author has afcertained the refiftance of bodies to all velo- 

 cities, from i to 2000 feet per fecond ; the bodies being 

 different, and their faces at different angles of elevation. 

 Some of his general tables, and conclufions from thofe expe- 

 riments, are as follows. 



Table I. Of Refiftances of different Bodies. 



In this table are contained the refiftances of feveral forms 

 of bodies, when moved with feveral degrees of velocity, 

 from 3 feet per fecond to 20 feet per fecond. The names 

 of the bodies are at the tops of the columns, as alfo which 

 end went foremoft through the air ; the different velocities 

 are in the firft column, and the refiftance, on the fame line in 

 their feveral columns in avoirdupois ounces and decimal 

 parts. Thus, on the firft line are contained the refiftances 

 when the bodies move with a velocity of three feet in a 

 fecond ; viz. in the fecond column, for the fmall hemifphere 

 of 4! inches diameter, its refiftance .028 ounces, when the 

 flat fide went foremoft ; in the third and fourth columns, the 

 refiftances to a large hemifphere, firft with the flat fide, and 

 next with the convex part foremoft ; the diameter of this, as 

 well as all the following figures, being 6 | inches, and there- 

 fore the area of the great circle = 32 fquare inches, or 4 of 

 a fquare foot ; then in the fifth and fixth columns are the re- 

 fiftances of a cone, firft, with its vertex, and then with its 

 bate foremoft ; the altitude of the cone being 6j inches, 

 the fame as the diameter of its bafe ; in the ieventh column, 

 the refiftance to the end of the cylinder ; and in the eighth, 

 that againft the whole globe or fphere. All the numbers 

 fhew the real weights which are equal to the refiftances ; and 

 at the bottoms of the columns are placed proportional num- 

 bers, which (hew the mean proportions of the refiftances of 

 all the figures to each other with any velocity, l.aftly, in 

 the ninth column are placed the exponents of the power of 

 the velocity which the refiftances in the eighth column bear 



to each other, viz. which that of the 10 feet velocity bears 

 to each of the following ones ; the medium of all them being 

 as the 2.04 power of the velocity ; that is, very little above 

 the fquare, or fecond power, fo far as the velocities in this 

 table extends. 



From this table the following inferences are readily de- 

 duced. 



1. That the refiftance is nearly in the fame proportion as 

 the furfaces ; a fmall increafeonly taking place in the greateft 

 furfaces, and for the greater velocities : thus, by comparing 

 together the numbers in the fecond and third columns for 

 the bafes of the two hemifpheres, the areas of which bafes 

 are in the proportion of 1 7^ to 32, or 5 to 9 very nearly, it 

 appears that the numbers in thefe two columns, exprefling 

 the refiftances, are nearly as I to 2, or 5 to 10, as far as 

 the velocity of 1 2 feet : but after that, the refiftances on 

 the greater furface increafe gradually more and more above 

 that proportion. 



2. The refiftance to the fame furface, with different velo- 

 cities, is, in thefe (low motions, nearly as the fquare of the 

 velocity ; but gradually increafes more and more above that 

 proportion, as the velocity increafes. This is manifeft from 

 all the columns ; and from the index of the power of the 

 velocity fet down in the ninth column for the refiftances in 

 the eighth, the medium of which being 2.04, fhews that the 

 refiftance to the fame body is, in thefe flow motions, as the 

 2.04 power of the velocity, or nearly as the fquare of it. 



3. The round ends, and the fliarp ends, of folids, fuffer 



lefs 



