104 THE CANADIAN NATURALIST. [April^ 



origin, such as apatite, and to the fossil bone-phosphate known 

 as coprolite ; and, secondly, in his having devised means and 

 appliances for carrying out the manufacture on an industrial scale. 

 Those upon whom it has devolved to organize a new industry, and 

 to overcome the difficulties that spring up, unforeseen, at every 

 stage of such a work, will know how to appreciate at their just 

 value Mr. Lawes's services in this respect. Indeed, in his double 

 capacity, as a manufacturer of manures, and as an indefatigable 

 experimentalist on their effects, Mr. Lawes merits recognition as 

 one of the most active promoters of agriculture now living. Nor 

 would it be just, in such a mention to overlook the large share of 

 service rendered by Dr. Gilbert, the able coadjutor of Mr. Lawes, 

 in the experimental and analytic department of his labors. 



Mr. Lawes appears to have made his first essays in the manu- 

 facture of superphosphate in 1841-2 ; and, on the success of these 

 experiments, to have begun his great manufactory at Deptford, in 

 1843. Many similar works have since sprung up, and the manu- 

 facture has grown to enormous magnitude. Mr. Lawes himself 

 produces 18,000 to 20,000 tons of superphosphate annually; and 

 the total yearly production of superphosphate in Great Britain is 

 estimated by him as ranging from 150,000 to 200,000 tons. 



Mr. Lawes has favored the Reporter with the following inter- 

 esting particulars as to the most recent and improved mode of 

 manufacturing superphosphate, its average composition, and its 

 present market price : — 



*' The phasphatic materials are first ground to a very fine powder 

 by millstones ; the powder is then carried up by means of eleva- 

 tors, and discharged continuously into a long iron cylinder, having 

 agitators revolving within it with great velocity. A constant 

 stream of sulphuric acid, of sp. gr. 1*66, enters the cylinder at the 

 same end as the dry powder, and the mixture flows out at the other 

 end in the form of a thick mud, havino; taken from three to five 

 minutes in passing through the machine. The quantity turned 

 out by such a mixing-machine is about 100 tons daily. The semi^ 

 fluid mass runs into covered pits ten to twelve feet deep, each of 

 sufficient siz3 to hold the produce of the day's work. It becomes 

 tolerably solid in a few hours, but retains a high temperature for 

 weeks, and even months, if left undisturbed. 



" The composition of a superphosphate, of good quality, made 

 partly from mineral phosphate and partly from ordinary bones, may 

 l)e stated as follows : 



