TESTIMONY OF BENJAMIN SILLIMAN. 117 



and the proportion of its parts, without any knowledge of the special 

 value of this particular sample of it, I should say it was a very well 

 devised form of hydrometer as applied to the measurement of milk 

 lactometer and for the reason that I specify, that the stem is very 

 slender and the bulb very large. 



Q. Will you give the reason as plainly as you can to the jury, 

 why the hydrometer is not as perfect and accurate a test for milk 

 as it is for other fluids ? 



(Objected to.) 



Q. Is the hydrometer as accurate a test for milk as it is for other 

 fluids, the specific gravity ? A. If I understand the question of the 

 learned counsel, it is a question as to whether the instrument is 

 capable, in dense fluids, of rendering as exact answers as in thin 

 fluids ? 



Q. No, sir ; it is a question of whether the hydrometer for 

 instance is as exact an instrument to test milk with as it is to test 

 alcohol ? 



Q. Is cream lighter than milk ? A. It is. 



Q. Is water also lighter than milk ? A. It is. 



Q. Does alcohol contain any impurity lighter than itself ? A. It 

 ought not to. 



Q. Pure alcohol I refer to ; is there not therefore a distinction 

 between the results of tests made of milk by the hydrometer and 

 tests of alcohol ? A. By the specific gravity test you may determine 

 density ? 



Q. Yes, sir? A. I conceive in no other sense than this, that if 

 the milk be carefully averaged so that the cream and the skimmed 

 milk be perfectly homogeneous, so to speak, in the mass, that there 

 is no serious error in the hydrometer as applied to the testing of the 

 density of milk more than applies to the use of the same instrument in 

 the testing of the density of oil or of any other substance that is more 

 or less viscous or tenacious, which is to be understood, if I may be 

 allowed to make the explanation, as involved in the care which is 

 used by those who have experience in the use of this instrument in 

 plunging it into the fluid that it be not wetted on any portion of the 

 stem above the point at which it is expected to sink, inasmuch as 

 in that case if it be so smeared or moistened by a dense liquid the 

 whole instrument becomes denser by that quantity and will sink 



