CHANGES IN VOLUME 39 



paraffin on a slide parallel to. one another. The layer of 

 paraffin between these strips and the slide was of excessive 

 thinness, as the strips were pressed firmly down on the 

 melted paraffin. The cover-slip with the drop of oil mixture 

 was then placed on the strips, and the water so far drawn 

 off from under it that the cover glass was firmly pressed 

 down upon the slips. Then the edges of the cover glass, 

 which rested on the glass strips, were firmly cemented with 

 melted paraffin from without. In this manner the distance 

 between the cover glass and the slide was kept sufficiently 

 constant, so that in the experiments to be described ia the 

 sequel, errors of any kind, through pressure of the cover 

 glass on the drops, appear to be excluded. ' 



Two preparations set up ia this manner contained each 

 three drops of the oQ mixture, which may be denoted by the 

 letters a, b, c, and d, e, f. 



On the 28th May, at 11 a.m.,. immediately after setting 

 up the preparation, the drops showed the following diameters. 

 The sign (m) added to the numerical statement indicates 

 that the drop ia question was not quite circular, so that the 

 statement represents the arithmetical mean of the greatest 

 and least diameter. 



I— Diameter ota = 0-720 (m) 

 6 = 0-488 

 c = 0-565 

 c^ = 0-385 

 6 = 0-469 

 /= 0-803 (m) 



At 6 P.M. on the same day the volume of the drops had 

 already much increased, and on the 29th May, at 10 A.M., it 

 had grown still more strongly, as shown in the following 

 table : — 



28/5. 6 p.m. 29/5. 10 a.m. 



II.— Diameter of a = 1-336 (m) 1-605 (m) 



& = 0-951 (m) 1-084 (m) 



„ c = 1-092 (m) 1-503 



c? = 0-707 0-784 



« = 0-925 0-997 (m) 



/= 1-388 1-481 



