OLEAGIKOUS PRODUCTS OF THAMES MUD. 265 



under the consideration of the more scientific of the Swiss agricul- 

 turists. Prom the mountain pasturages only milk is taken away, but 

 this milk contains a certain quantity of phosphates, the restoration 

 of which must be effected sooner or later, or the produce will be cut 

 off, especially now that so much condensed milk is exported. 



The wondrously rich soil of some parts of Virginia has been ex- 

 hausted by unrequited tobacco crops. The quantity of ash dis- 

 played on the burnt end of a cigar demonstrates the exhausting char- 

 acter of tobacco crops. That which the air and water supplied to the 

 plant is returned as invisible gases during combustion, but all the 

 ash that remains represents what the leaves have taken from the soil, 

 and what should be restored in order to sustain its pristine fertility. 



The West India Islands have similarly suffered to a very serious 

 extent on account of the former ignorance of the sugar planters, who 

 used the canes as fuel in boiling down the syrup, and allowed the 

 ashes of those canes to be washed into the sea. They were ignorant 

 of the fact that pure sugar may be taken away in unlimited quanti- 

 ties without any impoverishment of the land, seeing that it is com- 

 posed merely of carbon and the elements of water, all derivable from 

 air and rain. All that is needed to maintain the perennial fertility 

 of a sugar plantation is to restore the stems and leaves of the cane, 

 or carefully to distribute their ashes. 



The relation of these to the soil of the sugar plantations is pre- 

 cisely the same as that of the leaves of the trees to the soil of Ken- 

 sington Gardens, and the reckless removal of either must produce 

 the same disastrous consequences. 



CHAPTEK XXXVI. 



THE OLEAGINOUS PEODUCTS OP THAMES MUD : WHEEE THEY COME FROM 

 AND WHEBE THEY GO. 



ONCE upon a time and not a very long time since a French 

 chemist left the land of superexcellence, and crossed to the shores of 

 foggy Albion. He proceeded to Yorkshire, his object being to make 

 his fortune. He was so presumptuous as to believe that he might do 

 this by picking up something which Yorkshireinen threw away. 

 That something was soapsuds. His chemistry taught him that soap 

 is a compound of fat and alkali, and that if a stronger acid than that 

 belonging to the fat is added to soapsuds, the stronger acid will coin- 

 bine with the alkali and release the fat, the which fat thus liberated 

 will float upon the surface of the liquid, and may then be easily 

 skimmed off, melted together, and sold at a handsome profit. 



But why leave the beautiful France and desolate himself in dreary 

 Yorkshire merely to do this ? His reason was, that the cloth workers 

 of Yorkshire use tons and tons of soap for scouring their materials, 

 and throw away millions of gallons of soapsuds. Besides this, there 

 are manufactories of sulphuric acid near at hand, and a large demand 

 for machinery grease just thereabouts. He accordingly bought iron 

 tanks, and erected works in the midst of the busiest centre of the 



