USE OF GYPSUM. 125 



of gypsum, which has been the stumbling-block of chemists 

 for a great many years. I do not know exactly how it acts, 

 and cannot give directions how it should be applied. I only 

 know that gypsum, under very nearly all the circumstances 

 in which I have used it, I have found to be very valuable. 

 I think that gypsum needs a pretty large amount of water. 

 I think if we sow gypsum on our fields in a very dry season, 

 we do not get any very beneficial result from it ; but I think 

 if we sow it upon the same field, in a moist season, we do get 

 very good results. 



Another thing : I think that gypsum very nearly always 

 does well upon the north and north-east sides of hills. I 

 think it very seldom does much good upon the southern 

 slopes of hills. I have introduced that subject in conversa- 

 tion with a great number of farmers, and I found that that 

 seemed to be the view quite universally entertained by those 

 who have used it. Why it is so, I do not know ; only 

 I do know this : that the northern slope of hills is, of course, 

 longer in the shade than the southern slope, and there is 

 usually a heavier deposition of dew upon the northern slope 

 of hills. There is more moisture, usually, upon that slope 

 than there is upon the southern slope. 



I do not know that I can add anything to the stock of 

 knowledge regarding gypsum. I always keep it on hand ; I 

 always use it ; I have sent to Maine for it. I think there is 

 a difference in gypsum, and that some of it is of very little 

 value. I have examined two specimens of gypsum that were 

 very nearly half carbonate of lime, which is a form of sul- 

 phate of lime. Whether this was accidentally or designedly 

 mixed, I do not know. I have procured very fine gypsum 

 from Maine, and have found it to be very useful upon my 

 farm. I use it every year. I always use it in laying down 

 to grass. The amount we want to use is not large, because 

 you know that very little of it is soluble. It requires a very 

 large amount of water to render a very small amount of gyp- 

 sum soluble. Therefore, it is not necessary for us to sow it 

 thickly, but thinly, and sow it fine. These are all the facts 

 that I think are pertinent to this subject. 



Dr. Cogswell, of Bradford. The potato-crop is a crop 

 which interests, not only the farmer, but the whole com- 



