316 



THE TROPICAL AGRICULTURIST. 



[October i, 1884. 



25 per cent more valuable. Auy oue can understand this 

 double advantage of ash versus slag. The old man, my 

 opponent, on the result being explained to him, made a 

 remark in Gaelic, which was translated for me as 

 follows: — "I have been making kelp for fifty years and 

 more, and am I to be taught by a young Sassenach with 

 uo beard >>n his face to speak of?" That was the only 

 result of the experiment. How could I explain to him, 

 especially in Gaelic, the difference between specific gravity 

 and weight, to say notliiug of quality? As they would 

 not improve the process,, the work had to be stopped, and 

 their evideuce before the Koyal Commission shows how 

 much they have missed it. We took away their clauts, 

 but it was no use ; lauding once in the middle of the night, 

 I came upon a group hard at work with new irons, raking 

 off the salts, and making themselves hideous, for so intense 

 is the heat, that the soda volatised gives a strong mono- 

 chromatic yellow flame which does not improve the beauty 

 of tile workers. 



To show that this extraordinary idea still prevails, I quote 

 the following from a daily paper, referring to the island 

 of Tyree this year: — 



"The men attending the kilns used to turn over the 

 burning mass with iron 'clauts,' but about two years ago 

 the company forbade the use of the 'clauts,' and the kelp 

 is simply reduced to ashes instead of a hard substance. 

 It may be better fitted for manufacture in this state, but 

 it is also evident that it will take more of it to make a 

 ton than by the old process." 



It has oue advantage for them, being on the sandy shore, 

 or single, it enables them to rake in. and embody with 

 the fused kelp a quantity of sand and stones. We some- 

 times get a biock of granite thinly veneered with kelp from 

 our Irish friends, to remind us, I presume, of their national 

 wrongs, and take a slight revenge. 



The great heat involves the additional disadvantage that 

 the carbon reduces the sulphates to sulphides, which involve 

 considerable expenditure of oil of vitriol to decompose them, 

 so that sulphur thus deposited is one of the bye-products 

 of the lixiviation of kelp. We are therefore compelled 

 to reverse the ordinary process, and manufacture sulphur 

 from sulphuric acid. 



The usual yield of kelp from 100 tons of wet seaweed 

 is 5 tons, and as only half of this is soluble, 2i tons forms 

 the total valuable product of the labour of cutting, carry- 

 ing, drying, and burning 100 tons of wet seaweed; the 

 burner, in many parts, does not receive more than £2 per 

 ton, sometimes less, so that all this labour is done for 

 2s. per ton of weed. When it is also remembered that 

 bad weather often reduces this payment to nothing, it is 

 easy to understand that this occupation is soon given up 

 where any other employment can be obtaiued. Moreover, 

 the weed is dried in a climate where a native comes up 

 to you with the rain pouring off his hat and nose, and 

 outrages your sense of sight by informing you, if he knows 

 "tin English," that it is "a wee misty." The large mass 

 of material to be dealt with, the stormy character of the 

 coasts, the constant moisture of the climate, all tend to 

 still further reduce the quantity obtained. Even with 

 favourable conditions, the yield is only 5 per cent which 

 is quite inadequate to afford profit either to the maker 

 or to the lixiviator. 



These evils were fully pointed out in my former paper, 

 and a method was then suggested by which several new 

 products could he obtained, and the whole of the iodine 

 secured. I proposed to submit the seaweed to destructive 

 distillation in irou retorts, thus obtaining a loose, porous 

 charcoal, which retains the salts and the iodine; ammonia, 

 acetic acid, and tax- were obtained from the distillate. Iu 

 looking over the tables published iu my former papers, 

 some of the diagrams of wliich are once more on the wall, 

 I notice that the amount of iodine lost in kelp was much 

 under-estimated ; much too low a figure having beeu taken 

 for the produce of iodine. The amount of kelp then made 

 was 10,000 tons in this country, and 24,000 iu France; 

 and I estimated the loss of iodine, in this country alone, 

 at 50,000 lb. annually, it really was about three times that 

 amount, or 150,000 lb. worth, even at the present low 

 price, £37«500, a sum in excess of the whole value of the 

 ad litional new products proposed to be recovered. 



The Duke of Argyll was the first to see the value of 

 the improveiueut suggested, and the new process was first 

 carried out in his island of Tyree, iu 1803, where works 

 were erected for the purpose; soon afterwards works were 

 also erected in North I 'ist, under an arrangement with the 

 late proprietor, Sir .loun P. Orde; and more recently in 

 Ireland. J 



In some respects Tyree was the best place that could 

 have been selected, in others, the worst. The wildness of 

 its shores, and its numerous outlying rocks, make it the 

 deposit of much drift weed. The inaccessibility and the 

 great difficulty of lauding heavy machinery, &c, made the 

 erection of works extremely difflcu t. The factor calcul- 

 ated that 30,000 tous were used aunually for manure; 

 and that four times that q'uautity was lost. ( )ur calcul- 

 ations were based on recovering 16,U00 tons of this, aud 

 if even that quantity could have been obtained, the works 

 there would have had a very great success, and turned 

 out more iodine than all the other Highland shores put 

 together. It is impossible, however, to estimate the amount 

 ot seaweed thrown up in a storm, and the sea has an 

 awkward habit of calling again, and removing a good deal 

 of it, or covering it over with sand. This seaweed is also 

 much injured by rain, which soon washes out the salts and 

 iodine. It is a nitrogenous substance, aud is quickly devoured 

 by maggots, which become flies, aud the material, like some 

 other riches, speedily takes to itself wings and flies away, 

 so that when ouce I carted a large quantity to the works 

 for experiment, some knowing ones observed that the 

 Sassenach had taken a great deal of trouble to put in the 

 material, but it would not give him any kind of pains to 

 put it out, as it would leave him of its own accord. I 

 may add that it did not; there is nothing so offensive as 

 rotten seaweed, but I had preserved the weed with chloride 

 of calcium. In the winter the long sea rods are thrown 

 up, and these when properly stacked bear a good deal of 

 exposure. There was much difficulty in getting the people 

 to collect these at first, for it was a ncv thing, and they 

 did not believe in it. They soon found out, however, that 

 it affords winter employment for what they call "a lairge 

 sma ' family," and which, to do them credit, most of them 

 possess, as children cau work at it. It consists simply in 

 stacking the tangle out of reach of the tide. This work 

 has been going on ever since 18t>3, and none is lost that 

 cau be secured. The works in Tyree and in North Uist 

 are still continued, to the great advantage of the people. 

 For the latter the tangle is also collected in South Uist 

 and shipped to Loch Eport. Both these islands also yielded 

 large quantities of black-wrack kelp, which is now entirely 

 given up. 



The works were lighted with the gas obtained by distill- 

 ation, but after the gas has passed through all the purifiers, 

 it still burns with a strong monochromatic yellow flame. 

 The ammonia obtained is all used as manure for the farm ; 

 for whatever other business you follow in these outer 

 islands, you must be a farmer, to feed your horses, &c. 

 The tar is used for the roof of the works; and I may 

 state here, that after great experience of large roofs, many 

 of which have been blown away, I prefer a lattice girder 

 low felt roof. No one who has not witnessed a winter 

 gale in one of the Hebrides can from an idea of it. We 

 find it advisable to raise the walls two feet above the 

 girders on each side. I would also mention here that there 

 is no building so efficient or suitable for the damp climate 

 of these outer islands as concrete. The shingle of the shore 

 is always there as the bulk of the material, and cement 

 only has to be sent out. A vessel loaded with quick lime, 

 anchored off one of these islands in a gale, is not a 

 happy or a safe possession, and I know from expe- 

 rience that it does not contribute to the sweetness of 

 sleep. 



Iron retorts, heated by coal or peat, were at first used, 

 but these were superseded by brick ovens, which are now 

 employed without fuel. The tangle swells in the retort, 

 and produces a charcoal of great porosity, from which 

 the salts are easily washed out, and there are no sulphides. 

 The residual charcoal is a very efficient decoloriser and 

 deodoriser, but has never been largely used for these 

 purposes. I shall mention presently an application of it. 



The following analysis shows the comparison of this 

 charcoal with that from bone. It does not in any way 



