468 



Prof. Guthrie on Drops, 



[Rece&s, 



measured the temperature. Fully the upper half of the sphere was covered 

 with cotton-wool, so that the whole of the sphere was kept wet. The con- 

 siderable mass of mercury in the bulb of the dropping sphere or therm.o- 

 meter itself served to make more uniform the temperature of the drops ; 

 while the actual contact between the drops and the spherical bulb ensured 

 a tolerably close approximation between the actual temperature of the drops 

 and that indicated on the stem of the instrument. Although, therefore, 

 the temperatures observed cannot pretend to any even approximate positive 

 accuracy, yet they are certainly in the actual order of magnitude. The 

 arrangement is seen in Plate IV. fig. 6. 



Table Xll,— Water. 



r = 7'4 millims. 

 Number of drops = 20. 



Temperature, 

 Centigrade. 



Weight of 

 20 drops. 



Weight of 

 single drop. 



Eelative mean 

 size of single drop 

 (corrected for 

 temperature). 







grms. 



grm. 











2-5564 



0-12782 ■ 







40-3 ■ 



40- 



2-5795 



0-12897 



• 



0-12985 





37- 



2-5826 



0-12913 









(35- 



2-6083 



0-13041 ^ 









33-9 



2-6105 



0-13052 









32-6 



2-6161 



0-13080 









31-2 



2-5960 



0-12980 







. 30-6^ 



30-6 



2-6065 



0-13032 





0-13066 



29- 



2-6044 



0-13022 









28-2 



2-5983 



0-12992 









28- 



2-6078 



0-13029 









,27-5 



2-6032 



0-13016 ; 







20-4 



20-4 



2-6480 



0-13240 





0-13262 



In the above Table the temperatures are so grouped together that the 

 means of the groups differ from one another by about 10° C. The single 

 drop-weights are correspondingly grouped, and the mean of each group is 

 then divided by the specific gravity of water (0°=I) at the mean tempe- 

 rature of the group. 



It appears then that, for a range of 20° Centigrade, or 36° F., the dif- 

 ference in drop-size effected by change of temperature in the liquid is in- 

 appreciably small, not being more than 0-00277, a quantity almost within 

 the limits of experimental error ; for on referring to Table X. we find that 

 the greatest difference between the numbers for glass, which should be 

 equal, amounts to 0'00044 grm., or a sixth of the greatest difference due 

 to variation in temperature. 



On the whole, then, we may conclude that the temperature has very little 

 influence on the drop- size in the case of water bet\veen the above limits. 

 No doubt, near the point of solidification, where liquids have an incipient 



