1864] 



Prof. Guthrie on Drops. 



471 



fft=6". The drops were collected in a tube bearing an arbitrary mark. 

 The number of drops required to fill the tube up to this mark was noted. 

 Then the sphere was surrounded by turpentol, and the rate having been 

 brought again* to fft=5'\ the number of drops of water necessary to fill 

 the tube up to the same mark was counted. The turpentol being replaced 

 by benzol, the same operation was performed. The entire arrangement of 

 the Stalagmometerf is seen in Plate V. fig. 7. 



X, Y are contrivances described in Part I. for giving a uniform flow of 

 water. 



The siphon A rests upon the cotton-wool covering half of the dropping 

 sphere and thermometer-bulb G. The sphere is held by its stem B in the 

 clamp H. C is half a globular 1-lb. flask, supported by the filter-stand K. 

 Through the neck of C passes the tube D. C and D are joined liquid- 

 tight by the caoutchouc collar L. A few arbitrary marks are made at E. 

 The lip of C is turned down to a beak at M above the vessel F. 



In adjusting the instrument, to get the required value of fft, the holder 

 K is slipped along the table so that the drops from G fall between C and 

 D, and not into D. When the required rate is obtained, it is slipped back 

 again. When such liquids as turpentol are used as media, a little water 

 is poured between D and C to protect the caoutchouc. In all cases where 

 a liquid medium is employed C is filled till it runs over. 



In the first experiment, of which the results are given in the following 

 Table XIII., the numbers are subject to two sources of error. The volume 

 filled is rather small, and no allowance is made for meniscus. In this, as 

 in all cases of SLL, great care must be taken not to shake the instrument. 



Table XllL— Water. 

 fft=5". 

 T=22°C. 

 Radius of glass sphere = 7*4 millims. 



1. 



Medium. 



Air 



Turpentol 

 Benzol ., 



Number of drops of 

 water required to 

 fill a given Yolume. 



Mean of 

 Column 2. 



57-0 

 26-7 

 7-0 



4. 



Relative size of 



single drop 

 (through air=l). 



10 



214 



8-14 



There is therefore a greater difference between the drop-sizes of water in 

 benzol and turpentol than between those in turpentol and air. The tur- 



* A diminution of is observed. 



t 2raXa7/i6s, a drop. 



