THE NUTRITIVE VALUE OF OIL-CAKES, ETC. 61 



Professor VOELCKEB. Even yellow clays have different qualities. It is diffi- 

 cult to answer this question without knowing the description of clay. Now, I 

 have seen superphosphates fail on stiff clay lands, not that they were not wanted, 

 but from other causes ; yet if 1 were to say 1 had tried it, and see no use in 

 superphosphate, you would say I generalised on false premises ; and if I say it 

 is very useful on all lands, you would say I knew nothing at all about it 

 (laughter). But this is a question on which I can give you some information. 

 Some time since I made some experiments with superphosphates, in order to 

 ascertain the quantity most useful to apply ; I began with 1 cwt., then 3 cwt., 

 then 6 cwt., up to a ton. My object was, not so much to get a good crop, as to 

 ascertain what would be the quantity produced under similar circumstances ; 

 ane also whether you can kill seed with the manure. It is a curious fact that 

 you cannot kill seed with it ; but guano and sulphate of ammonia, in excess, 

 will kill seed. Experiments were made to ascertain the effects of the chief fer- 

 tilising matters ; and sulphate of ammonia, used in moderately large quantities, 

 retarded the germination of seed in a remarkable manner, whilst the phosphate, 

 instead of retarding it or killing it, made it sprout all the quicker. It is a very 

 remarkable fact. I tried the experiments with the superphosphate on a portion 

 of our farm at Cirencester, which had not been taken into cultivation. It is a 

 description of soil very similar to the one which you have described a yellow 

 stiff clay. On this soil superphosphate produced no effect (hear, hear). I did 

 not get 50 Ibs. an acre more in those parts where I had put a heavy dose of 

 superphosphate. Now, if I had not also made a little experiment on pulverised 

 soil, I might have come to the conclusion that superphosphate on clay soils is 

 of no use (hear, hear). You must be very careful how you generalise on a 

 single fact. I veiy soon discovered why the superphosphate was of no effect 

 on the yellow clay ; it was because the land was not sufficiently pulverised 

 (applause). Never use superphosphate on land that is not in a high state of 

 pulverisation. Many useful manures are wasted by application to land not 

 properly pulverised. The introduction of proper manure requires the use of 

 improved implements (applause). Hence it is that some manure-manufac- 

 turers sell improved implements, without a profit, to purchasers of their manures, 

 because they know that with the supply of an improved class of implements for 

 pulverisation, the success of their manure is secured ; and the more those imple- 

 ments are used, the better sales their manures meet with (applause). The 

 Professor then, in reply to Mr. Wills, stated concerning the application of lime 

 to moor-land (granitic) soils which produced much clover, that granite was 

 composed of felspar, mica, and silex, and that by the application of lime the 

 felspar was decomposed. The lime set free the potash, which was largely re- 

 quired by the clover plant. 



4. THE NUTEITIVE VALUE OF OIL-CAKES, &o. 



[Delivered at Exeter, January, 1857.] 



ON Friday, January 23rd, the following Lecture was delivered 

 at the Athenseum, Exeter, on the " Nutritive Value of different 

 Oil-cakes and Substitutes for Oil-cakes." The Major, \V. 

 BUCKINGHAM, Esq. presided. 



The PROFESSOR said Gentlemen, last year I had the plea- 

 sure of delivering a lecture, in this room, on the principles of 



