October i, 1884.] 



THE TROPICAL AGRICULTURIST. 



3'5 



about 2 per cent. Professor Dittmar, who has been work- 

 ing out the seawater samples of the Challenger expedition, 

 has discovered a remarkable relation between this element 

 and that of the chlorine which he has kindly communic- 

 ated to me. He finds the relation in the great number 

 of samples examined (77) to be constant in the proportion 

 of '340 bromine to 1U0 chlorine. He finds the average 

 amount of chlorine to be 1"9 per cent, or 19,000 parts in 

 1,000,000 and of bromine -00640 per cent, or 64-6 parts 

 in 1,01(0,000, or 18,422 times as much as my mean result for 

 the iodine. The Woodal Spa has been long known to be 

 very rich in iodine and bromine ; a recent analysis by 

 Wright giving of chlorine 1111373 parts per million, brom- 

 ine 49*7 parts per million, iodine 521 parts per million. 

 Here the relation of bromine to chlorine is -44 to 100, 

 and the iodine about a tenth of the bromine ; in seawater 

 the proportion of iodine is a very minute fraction of this. 

 Examination of the brine and the mother liquor from the 

 salt mines of Cheshire failed to detect iodine. The alga? 

 possess the power of assimilating the iodine to about ten 

 times the extent of the bromine. I append estimates of 

 iodine in a number of algre, those of the Laminaria and 

 Fuci are the average of a great number of specimens 

 collected at different times of the year, and all round 

 Great Britain aud Ireland, the Channel Islands, and the 

 Isle of Man, and including Orkney and Shetland, Iceland, 

 Denmark, and Norway. I append also estimate of the 

 iodine in several of the giant alga? in the Falkland Islands, 

 for which I am indebted to Governor Kerr, and Mr. F. G. 

 Cobb, of the Falkland Islands Company. 



These gigantic species are seen in this country for the 

 first time in the fresh state, and little is known about them. 

 The macrocystis is said to grow to a length of 1,500 ft., 

 or over a quarter of a-mile in length. It grows in 10 fathoms 

 water in Stanley harbour. 



The iVUrvillea forms stems branched like trees 12 ft. or 

 14 ft. long, and a foot in diameter. All these weeds are 

 thrown up in enormous quantities on the shores of the 

 Falkland Islands, aud along the Straits of Magellan, making 

 it difficult for a boat to approach them. 



DRV WEEDS. 



Per cent. 



Laminaria IHgitata, tangle stem ... 0'4535 



., „ Bardarrig frond 02940 



„ Stenophylla stem 0-4028 



„ „ frond 0-4777 



., Saccharina, sugar wrack ... 0'2794 



„ Bulbosa 0-1966 



Fucus Serratus, black wrack 0'0856 



„ Nodosus, knobbed wrack ... 0-0572 



„ Vesiculosus, bladder wrack ... 00297 



Halidrys Siliquosa, sea oak 0'2131 



I 1 ynianthalia Lorea, sea laces 0'0892 



Rhudumeuia Palmata, dulse 0'7120 



Japanese edible seaweed 0'3171 



Zostera Marina -J £ at : order \ ... 0-0457 

 ( Zosteraceu; J ' 



Khodomela pinuastriodes 0'0378 



Chordaria flagelliformis 2810 



Chorda filum, sea twine 0'1200 



Ohoudrus crispus, Irish moss Trace 



Enteromorpha compressa, sea grass Nil 



Gelideum corneum, Japan Trace 



„ „ Cornwall „ 



Euchemia spinosa (agar agar) Nil 



FALKLAND ISLANDS GIANT ALOJE. 



lb. f ton. 



10-158 

 6-599 

 9-021 



10-702 

 6-258 

 4- 103 

 1-807 

 1-281 

 ■665 

 4-773 

 1-998 

 1-594 

 7-102 



1-023 



•468 

 6-294 

 2-688 



D'Urvillom utilis, 

 Lessonia 



No. 

 Xo. 

 No. 

 No. 



Macrocystis Pyrifera 



Per cent. lb. f ton. 



1 ... 00075 ... -179 



2 ... Trace ... — 



1 ... 00284 ... -636 



2 ... 00181 ... -405 

 0-0308 ... -690 



In the foregoing table the Laminaria; and the Fuci are 

 the kelp-producing species. 



It is remarkable that the three gelatinous species, Ohn,i,/,-us, 

 Gehdeuiur. and Euchemia contain little or no iodine. 



It is noticeable, too, that the Enteromorpha, or sea grass, 

 a plant which retains, when dry, a very storng odour of 

 the sea, contains no iodine. 



It is also remarkable that the giant aiga? contain so little 

 iodine, growing outside the influence of the Gulf Stream, 



which, rightly or wrongly, has been supposed to be the 

 iodine carrier. It is a curious fact that there are certain 

 seeds, supposed by the natives to grow on the tangle, 

 and called "tangle nuts." A specimen here from Tyree is 

 evidently the seed of a leguminous American tree, brought 

 over by the Gulf Stream. 



It is probable that all animal substances from the sea 

 contain iodine; its presence has been long known in cod-liver 

 oil, a substance supposed to be rich in it, and to owe mosl 

 of its valuable medicinal property to it, but I found, after 

 investigating a good many various specimens of this oil, 

 that the amount is infinitesimal. The liver itself contains 

 double as much; oysters, especially the Portuguese variety, 

 have also been said to contain a good deal. The following 

 are my results: — 



Cod-liver oil, average of six specimens.. 



Cod-liver, fresh 



Salt cod fish 



Salt ling fish ... . 



Fresh cod fish 



Scotch herring, salt ., 

 Scotch herring, brine 

 Oysters, Portuguese.. 



AVhale oil 



Sea oil 



48'5 per cent water 

 50-25 „ „ . 



80-7 „ „ . 



Per cent. 

 . Wi;y2 

 . -01 II INI 7 

 ■000255 

 . -000150 

 . -000160 

 . -0OU650 

 . -000120 

 . 000040 



. -oooioo 



■I II II II I,",! I 



There are two distinct and well-defined varieties of kelp. 

 Cut weed or black-wrack kelp, and drift weed or red-ware 

 kelp. Cut weed kelp is the old soda-producing variety, and 

 is made from the three Fuci. Funis vesiculosus, F. unclosus, 

 and !•. serratus; these grow on the rocks in the order named, 

 the latter being the most submerged aud containing the 

 most 'odine, though all contain but little. The plants are 

 cut at low tide, floated ashore, dried and burnt; the weed 

 does not soften much by rain, and it can always be obtained 

 ii. the fine natural harbours of the West of Scotland and 

 Ireland. This kelp, burnt into a dense fused slag, contained 

 the most carbonate of soda, and was that variety which 

 employed so many poor crofters and cottars, and enriched 

 so many highland lairds. It is now worthless, aud the Fuci, 

 which hang from the rocks at low water in luxurious festoons 

 in these lochs, are now entirely unutilised. I have seen 

 10,000 tons of this weed cut in a single loch, in a few 

 weeks of summer. 



The drift kelp is made from two varieties of red weeds, 

 or Laminaria, the L. Digitata, and the L. Stenophylla, the 

 former known as tangle; both are always submerged, and 

 are torn up by the violent gales, so common on the west 

 coast; both are sometimes cut in Ireland with long hooks 

 under water from boats These plants, especially the latter, 

 suffer very much from rain, and are often, after drying, 

 almost valueless; but if well saved, contain ten times as 

 much iodine as the Fuci. 



This is the only kelp now used for making iodine, and 

 it ought to be burnt into a loose ash; but although they 

 employ a different material we have to deal with the same 

 people, and they still insist on raking it into a molten 

 slag, with iron clauts, at great extra trouble, so much so 

 that the men of the family are obliged to do this part 

 of the work, under the erroneous impression that it will 

 weigh heavier, thus mistaking specific gravity for weight; 

 the fact being that they drive off more than half the 

 iodine, and a great deal of the salts, spending several extra 

 laborious hours in reducing the value to a half. It may 

 be asked why we allow it? An incident which occurred 

 to me may answer that question. 



Some years ago, when I had to take a large quantity 

 of black-wrack kelp in North Uist, it was made to enable 

 the people to pay their rents, aud could not then be given 

 up, though it has been since. I tried hard to get some 

 improvement made in the direction of burning the weed 

 at a lower temperature. The people were assembled in 

 great numbers, and the sheriff eloquently harangued them 

 in Gaelic for me. Their objections were threefold: it woidd 

 not yield so much, it would not be so good, and it would 

 take too loug. The late Sir John P. Orde, the proprietor, 

 and his factor were present, and it was agreed at last that 

 the most experienced kelper and myself should try the 

 experiment, each to have a certain quantity of weed weighed 

 out to him. and each to burn it his own way. As I ex- 

 pected, my lot was finished first. The yield was 25 per 

 cent greater, and the product was also, weight for weight. 



