TESTIMONY OF BENJAMIN SILLIMAN. 129 



degrees by the lactometer, the volume of cream so added will be 

 necessarily very large, and that the effect upon the milk will conse- 

 quently be very apparent, whereas 5 per cent, of water might be 

 added which would reduce the density of milk to 95 in round num- 

 bers, and its effect might not be very apparent ; it would be a little 

 thinner, but would not be very apparent. 



Q. Professor, as you have just stated that the specific gravities 

 of cream and milk were nearly alike, how can you now state that a 

 large quantity of cream would only bring the milk down 5 per cent. ? 

 A. I think I have sufficiently explained that. 



Q. How large a quantity would have to be added ? A. In a par- 

 ticular case which occurs to my memory, milk which had the density 

 of 1.018 by specific gravity determined by the balances was found 

 to have 55 per cent, by volume of cream floating upon it after stand- 

 ing until the cream was raised ; I therefore infer that in order to 

 reduce the density of milk to 1.018 that at least one-half its volume 

 must be cream. 



Q. If you see a cow milked and its milk stands at a low gravity, 

 at as low a gravity as you ever find pure healthy milk, can you tell 

 whether that low gravity is caused by the presence of much cream 

 or much water in the milk ? A. I think so. 



Q. How can you tell that ? A. By the sensible properties of 

 the fluid. 



Q. Can you tell it from the exercise of the senses ? A. In con- 

 nection with the lactometer ; you assume it is of a like density ? 



Q. Yes, of course I do ? A. The reason for my answer is this : 

 a cow in health never gives milk of a low density, which usually 

 means an excess of cream, unless she has been fed upon highly 

 oleaginous food ; if she is a stall-fed cow, fed upon cotton seed 

 meal or upon linseed meal or very nutritious food, her cream may 

 be very greatly exaggerated. 



Q, Then I understand you at last definitely that if you see a 

 sample of milk which you know to be pure milk at a low gravity and 

 apply the lactometrical test properly and exercise the senses you 

 can thus determine whether the low gravity is due to the water or to 

 cream ? A. I think so and for the reason that the analysis of that 

 very milk which I cite showed only 80 per cent, of water. 



