1864.] 



Prof. Guthrie on Drops. 



461 



by a system of spheres of various radii, but made of the same material. 

 And this case is an important one, because it undoubtedly offers the key 

 to all drop-size variation arising from a similar cause. To study this point 

 we may make use of any one convenient liquid, such as water, and cause 

 it to drop at a fixed rate from spheres of various radii, including the ex- 

 treme case of a horizontal plane. This extreme case, however, presents 

 certain practical difficulties. From a plane it is almost impossible to get 

 a series of drops uniform in growth-time and in position. A ripe drop 

 hanging from a horizontal plane will seek the edge thereof. Several drops 

 may form upon and fall from the same plate at the same time and inde- 

 pendently of one another. It is only by employing a plate not absolutely 

 flat, that an approximation to the required conditions can be made. Taking 

 r for the radius of curvature, the first numbers for r=co can therefore be 

 considered only as an approximation. The arrangements for the other 

 cases were quite similar to that described in Part I., fig. 3. 



No. 1. A glass plate, fastened to and held by a vertical rod. 



Nos. 2, 3, 4. Selected globular glass flasks. 



Nos. 5, 6, &c. Perfectly spherical glass spheres. 



Table \Ul.— Water, 

 T=22°-5C. 



1. 



2. 



3. 



4. 



5. 





Number 

 of drops. 



Eadius of 

 curvature. 



Weight 

 of drops. 



Mean weight 

 and relative size 

 of single drop. 



1. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 



{i} 



{IS} 



{iS} 

 {'%\ 



00 



mm. 



113-1 

 70-1 

 47-2 

 17-5 

 15-1 

 li-5 

 11-2 

 10-0 

 7-5 

 7-1 



\ 

 \ 

 \ 

 \ 



' 

 \ 

 \ 

 \ 

 1 



arm. 



'5-33251 



5-2873/ 

 "4-92261 



5-0007 / 

 ^4-52601 



4-5218/ 

 ' 4-2781 1 



4-2249 / 

 '3-50551 

 L 3-4733/ 

 r 3-35621 

 [3-3500/ 

 r 3-02811 

 [3-0206/ 

 [2-98031 

 [2-9780/ 

 [2-86651 

 [2-8619/ 

 [2-67651 

 [2-6660/ 

 [2-57521 

 [1-1591/ 



0-26549 

 0-24808 

 0-22619 

 0-21257 

 0-17497 

 0-16765 

 0-15122 

 0-14896 

 0-14321 

 0-13356 

 0-12877 



It appears, therefore, that the drop increases in size according as the radius 



