188 



HISTORY OK THE VEGETABLE KINGDOM. 



the duty on muriate of soda or common salt. 

 The rock salt of Cheshire, which now bears an 

 insignificant price, is submitted to a chemical 

 process, by means of which the soda is separated 

 from the muriatic acid ; and this is found to answer 

 so completely as a substitute for kelp, that the 

 great glass manufacturers of Newcastle are sup- 

 plied with soda thus prepared. So pernicious, 

 however, are the fumes of the muriatic acid gas 

 which issue from the soda works, that vegetation 

 is destroyed to a considerable distance; and the 

 proprietors have been compelled to purchase the 

 ground in the immediate neighbourhood. 



The number of people that find occupation in 

 the manufactui-e of kelp is so great, that a per- 

 manent interruption to the trade would be a 

 serious evil. In the Orkney islands alone, the 

 number of hands employed a few years ago 

 amounted to probably 20,000; for all the rural 

 population is more or less employed in the busi- 

 ness during the kelp season. Such being the 

 case, it is gratifying to find that the Highland 

 society have instituted inquu-ies regarding the 

 qualities of kelp as a manure. It has long been 

 known that common sea ware is extremely val- 

 uable for that purpose; and if the success which 

 has attended the experiments already made with 

 keljj, be confirmed by additional observation, 

 the manufacture may still be regarded as an im- 

 portant article of domestic commerce. 



It appears from communications made to the 

 highland society, that the past success has been 

 such as to induce Lord Dundas to take a cargo 

 of fifty tons of kelp to Yorkshire, for the sole 

 purpose of agricultural experiments. It has 

 been tried as a top dressing, and singly, or in 

 combination with other manures, on com, pas- 

 ture, potatoes, turnips, &c., and in most instances 

 with decided good effect. The committee ap- 

 pointed to collect the result of the experiments, 

 are inclined to think that, for raising green crops 

 it would be better to compost it with other sub- 

 stances; that with good earth or moss, and a little 

 vegetable or animal manure, a few tons of kelp 

 would enable a farmer to extend his farm dung 

 over at least four times the usual quantity of 

 land. A very curious circumstance is mentioned 

 by Mr M'Intosh, who tried the effects of kelp 

 manui-e on potatoes, at Crossbasket near Glas- 

 gow. A severe frost which occurred in Sep- 

 tember injured and blackened every lot of po- 

 tatoes to which the kelp had not been applied, 

 while the kelp lots remained in perfect foliage, 

 even when the respective drills were contiguous. 

 It would appear that the soil for the time being 

 had acquired a property equivalent to a certain 

 degree of atmospheric temperature; or ratJier 

 that the nourishment absorbed by the plants 

 under such circumstances, had enabled them to 

 resist a degree of cold that would otherwise 

 have destroyed them. 



The alga; grow very rapidly, and the pro- 

 duce is far less exposed to casualities than the 

 crops of the agriculturist in so precarious a 

 climate as that of the Hebrides and Orkney 

 islands. While in some places the sea weed is 

 cut only every third year, in others, especially 

 where there are strong currents, an annual har- 

 vest may be obtained without injury. The ra- 

 pidity of growth in the larger algfe, is indeed 

 wonderful. When Mr Stevenson the engineer 

 was erecting a lighthouse on the Carr rock, in 

 the Firth of Forth, which rock is about sixty 

 feet long and twenty broad, and onl}^ uncovered 

 at low water, he had occasion to remark the 

 quick renewal of the sea tangle with which it 

 was covered. In the course of the autumn of 

 1813 the workmen had succeeded in clearing out 

 and levelling with the pick and axe a consider- 

 able part of the foundation of the intended bea- 

 con, when, in the beginning of November, the 

 operations were necessarily abandoned for the 

 winter. At this time the rock was reduced to 

 a bare state; the coating of sea weed had at first 

 been cut away by the workmen; the roots or 

 bases were afterwards trampled by their feet; 

 and much of the surface of the rock had been 

 chiselled. Upon returning to the Carr, in May 

 1814, in order to recommence operations, it was 

 matter of no slight surprise to find the surface 

 again as completely invested with large sea 

 weeds as ever it was; although little more 

 than six months had elapsed since the work had 

 been left off, when, as already said, the rock had 

 been cleared of weeds. In particular, it was 

 observed that many new produced specimens of 

 fucus esculentus measured six feet in length, and 

 were already furnished with the small appen- 

 dages near the base or pinnae, which, at maturity, 

 contain the seeds of the plants. The common 

 tangle was generally only about two feet long. 

 It may be observed that the specimens here al- 

 luded to, were taken from that part of the sur- 

 face of the work which had been dressed off with 

 the pick and chisel the preceding autumn; they 

 had therefore grown from the seed. 



Every zone of the earth presents a peculiar sys- 

 tem of existence; and it is said that after a space 

 of 24° of latitude, a nearly total change is ob- 

 served in the species of organized beings, and 

 that this change is chiefly owing to the influence 

 of the sun. Lamouroux remarks, that if this 

 holds good, as is certainly the case in phoeno- 

 gamous plants, temperature should also exert 

 some corresponding influence upon marine vege- 

 tation. It is beyond doubt that the algse are 

 found upon the British coasts in greatest abun- 

 dance during the summer months, and in un- 

 usual luxuriance during hot seasons. It is pro- 

 bable also, the same author observes, that these 

 plants may be acted on by the temperature of 

 the water at greater or less depths; and that those 



