356 COMPOSITION AND USE OF KELP. 



Islands, but the low price at which carbonate of soda can now be maa« 

 ufactured has so reduced the price and the demand for kelp as almost 

 to drive it from the market. As a natural mixture, however, which 

 can now be obtained at a cheap rate (about c5£3 a ton), and which has 

 been proved to be useful to vegetation in a high degree, (Prize Essays 

 ot' the Highland Society, vols. 1 and 4,) it is very desirable that accu- 

 rate experiments should be instituted with the view of determining the 

 precise extent of its action, as well as 'the crops and soils to which it can 

 be most advantageously and most economically applied. 



Like wood ashes, kelp varies in composition with the species and age 

 of the marine- plants (sea weeds) from which it is prepared, and like 

 them also it consists of a soluble and insoluble portion. Two samples 

 from different localities in the Isle of Skye, analyzed by Dr. Ure, (Dic- 

 tionary of Arts and Manufactures, p. 726), consisted of — 



Normandy, 

 Soluble Portion. Heisker. Rona. Gay-Lussac. 



Carbonate of Soda with Sulphuret of Sodium . 85 5-5 — 



Sulphate of Soda 80 190 — 



Common Salt ^ qc f; ii r, 5^^'^ 



Chloride of Potassium $ "^^ ^''^ {250 



530 620 

 Insoluble Portion. 



Carbonate of Lime 240 100 — 



Silica 8-0 — — 



Alumina and Oxide of Iron . . . . 9 100 — 



Gypsum — 95 — 



Sulphur and loss 60 8-5 — 



100 100 



Besides these constituents, however, the soluble portion contains 

 iodide of potasium or sodium in variable quantity, and the insoluble 

 more or less of potash and soda in the state ot silicates. 



Kelp may be applied to the land in nearly the same circumstances as 

 wood-ash — but for this purpose it would probably be better to burn the 

 sea weed at a lower temperature than is usually employed. By this 

 means, being prevented from melting, it would be obtained at once in 

 the state of a fine powder, and would be richer in potash and soda. 



It might lead to important results of a practical nature, were a series 

 o^ precise experiments made with this finely divided kelp as a manure* 

 — especially in inland situations — for though the variable proportion of 

 its constituents will always cause a degree of uncertainty in regard to 

 the action of the ash of marine plants — yet if the quantity of chloride 

 of potassium it contains to be on an average nearly as great as is stated 

 above in the analysis of Gay-Lussac — kelp will really be the cheapest 

 form in which we can at present apply potash to the land. 



e. Straiv ashes. — The ashes obtained by burning the straw of oats, 

 barley, wheat, and rye, contain a natural mixture of saline substances, 

 which is exceedingly valuable as a manure to almost every crop. The 



' For some other suggestions on this subject, I beg to refer the reader to the Prize Et- 

 tays and Transactions of the Highland and Agricultural Society, xiv., p. 503. 



