Mr. T. Tate's Experimental Researches on Absorption. 133 



4. Under constant pressure, the rate at which a siphon-filter 

 transmits water is nearly the same for all lengths of the filter, 

 provided the length is not less than a certain minimum corre- 

 sponding to a maximum of discharge. 



Let KAB (fig. 4) be a siphon-filter of calico, 

 transmitting water from the tube of the second 

 absorbometer which has been described ; A B a 

 glass cylinder nearly filled with water, in which 

 the lower end of the filter is inserted. By 

 lowering or elevating the cylinder, any proposed 

 length may be given to the filter, and the times 

 required for discharging a cubic inch of water 

 from the tube D at the different lengths of 

 the filter can be accurately ascertained. Thus 

 it was found that the times requisite for the 

 discharge of one cubic inch of water were as 

 follows : — 



viz. 25 minutes with a filter 



20-5 „ „ 6 



20 „ „ 8 



20 „ „ 13 



20-3 „ „ 25 



3 inches long- 



Here the minimum length corresponding to maximum dis- 

 charge exceeds 3 inches ; but for lengths of filter exceeding this, 

 the rate of discharge is very nearly constant. The filter in this 

 experiment was fine cloth H inch in width. 



5. When a portion of the filter of the last experiment is placed 

 horizontally, the rate of discharge (with a certain proviso) varies 

 inversely as the length of this horizontal portion. 



The results of experiment were correctly represented by the 

 formula 



38-2 

 V= LT5' 



where L is put for the length of the horizontal portion in inches, 

 and v is the corresponding weight of the discharge of water in 

 grains per minute. 



Here a constant is added to the actual length of the horizontal 

 portion of the filter, this constant being the distance due to the 

 initial velocity; when L = 0, the initial velocity is 7'6. When 

 L was 12 inches, the rate of discharge per minute was found to 

 be 2*25, which by the formula would be 2'24; when L was 6 

 inches, v was found to be 3*53, which by the formula would be 

 3*47; when L = 36 inches, v was found to he 4*49, which by 

 the formula would be 4*44; and so on. 



6. When a siphon-filter transmits water under a reduced prcs- 



