VALUE OF ARTIFICIAL MANURES. 43 



productive to the root crop than superphosphate. He was, therefore, anxious 

 to have that question decided. 



Professor VOELCKER thought there could he no question ahout the efficacy of 

 guano both in the cultivation of the turnip and wheat crops. Experience had, 

 however, shown that phosphates were peculiarly valuable in the root crops. It 

 mattered little whether they were in bone-dust or guano ; but the question was 

 in what form could we get them cheapest, and he thought that if they bought 

 a good superphosphate, they must necessarily get phosphate cheaper than they 

 could get it in guano. Now he had come to this conclusion from experiments 

 which he had prosecuted, that a small quantity of ammonia was extremely 

 useful for the turnip crops. As a manure, they would find 3 cwt. of super- 

 phosphate and 1 cwt. of guano very good ; but if they depended entirely on their 

 guano as a manure for their turnips, they would throw away the greater part 

 of the most valuable commercially speaking constituent, namely, ammonia. 



Mr. How asked what percentage of soluble and insoluble phosphate should a 

 superphosphate contain to be a good and genuine article ? 



Professor VOELCKEE said it must be the object of the manufacturer to pro- 

 duce soluble phosphate, which was a material the farmer could not produce 

 conveniently. It might answer in certain cases to mix bone-dust with it; 

 but this the farmer could do himself. The value of phosphate depended 

 principally upon the amount of soluble phosphate it contained ; and the more 

 soluble it contained the more the manufacturer had a right to expect for it. 



Mr. How repeated his question, upon which 



Professor VOELCKER said he ought to frame his question in this manner 

 What ought a manufacturer to charge for a quantity of soluble phosphate ? 



Mr. How did not understand what amount of soluble and insoluble phosphate 

 a ton of superphosphate should contain. 



Professor VOELCKER said it would depend upon the price. 



Mr. How. Say SL a ton. 



Professor VOELCKER said perhaps the gentleman who had put the question 

 would forgive him if he declined answering it, because it would be injudicious 

 to interfere with the trader in his competition with others of his class. The 

 more soluble phosphate superphosphate contained the better; and let those 

 who could supply the larger quantity of soluble phosphate get the best sale for 

 it. It was not the business of the chemist to fix prices, but to guard farmers 

 against being grossly taken in. 



Mr. GREGORY could not help bringing to his recollection the fact that when 

 the London Economical manure, which had been referred to by the learned lec- 

 turer, first came out, the books which were published in its favour contained 

 copies of testimonials from persons who had tested it and who alleged that it 

 answered ; but when it appeared it was almost useless. He made these remarks 

 to assure the meeting that testimonials were often a perfect humbug. 



Mr. YOUNG (manure-merchant) had been exceedingly gratified with the 

 lecture, and he believed every one present could similarly express himself ; but 

 he would mention that they in that part of the kingdom had but very few 

 opportunities of meeting with a gentleman so well acquainted with agricultural 

 subjects to afford the information they required. He believed that bones con- 

 tained, besides phosphate of lime, another matter known by the name of gela- 

 tine, which he understood was considered of some value. There were manu- 

 facturers, however, who extracted from bones this gelatine, which they sold for 

 the purposes of sizing. He asked if it was not advisable to make one-half of 

 the phosphate of lime soluble and the other half insoluble ? 



Professor VOELCKER would leave that question entirely to the judgment of 

 the manufacturer and the farmer to find out which answered them best. 



Mr. Gr. H. COTTON said that it had been stated that it was desirable to mix 

 guano witff common salt or burnt clay. As common salt was a cheap article, 

 it occurred to him that farmers would be glad to know in what proportions the 

 lecturer would recommend it to be mixed. 



