INDUSTRIES 



This is the origin of the ' stream tin ' deposits in 

 the valleys of Cornwall, especially those to the 

 south of the watershed, and, to a lesser extent, 

 in the valleys of the Dartmoor rivers. 



Probably attention was first directed to deposits 

 of stream tin by an agency similar to that lead- 

 ing to their formation. Streams and rivers, 

 swollen by rains, would cut deeper gutters 

 through the alluvium of their valleys, and expose 

 layers of tin stones, pebbles, and gravel. What 

 was thus shown to occur in several valleys would 

 be anticipated and sought in similar situations 

 elsewhere, although the surface indications might 

 not precisely correspond or be so decisive ; and, 

 by degrees, discovery would become an art. 

 Nor could stream works be long in operation 

 without some evidences of their connexion with 

 the lodes in adjacent hills. The early miners 

 might not recognize the fact that the quantity of 

 tin stone washed down into the valleys and 

 moors was a measure of the denudation of the 

 more elevated regions of the country; but they 

 could not fail, as they worked upward, to dis- 

 cover some traces of the veins from which stream 

 tin had been derived. Hence, unquestionably, 

 arose the practice of ' shoding.' J 



'The ores of tin,' wrote Pryce in 1778," 

 ' are shode, stream, and mine. The shode is 

 adjacent to and scattered to some distance from 

 its parent lode, and consists of pebbly and 

 smoothly angular stones of various sizes, from 

 a half-6unce to some pounds in weight. Stream 

 tin is the same as shode, but smaller in size and 

 arenaceous, and in that state is formed of small 

 pyramids of various planes, broad at the base and 

 tapering to a point at the top. Stream tin ore is 

 the smaller loose particles of the mineral de- 

 tached from the bryle, or backs of sundry lodes, 

 situated on hilly ground, and carried down into 

 the vales by the retiring waters of the floods. In 

 the solid rock of the valley there is no tin ore, 

 but immediately upon it is deposited a layer of 

 stream tin of various thicknesses, perhaps over 

 that a layer of earth, clay, or gravel, and upon 

 that another stratum of tin ore, and so on suc- 

 cessively, stratum on stratum, according to their 

 gravity, and the different periods of their coming. 

 Mine ore,' he goes on to say, ' is the original 

 lode, buried usually in rocky substances in the 

 hills or the cliffs.' 



We cannot end this description of the tin beds, 

 so essential to the proper understanding of the 

 history of Cornish mining, better than by an 

 account of an old stream work discovered about 

 a century ago, and mentioned by the historian 

 Polwhele. 'They (the Forth stream works) 

 were situated near the shore of Trewardreth 

 Bay ; the ore was of the purest kind, and con- 

 tained two-thirds metal. The pebbles from which 



1 Worth, Historical Notes concerning the Progress of 

 Mining Skill, 5. 



1 Pryce, Minerahgia Cornubiensis, 66. 



the metal was extracted were in size from sand- 

 like grains to that of a small egg. They were 

 included in a bluish marl, mixed with sand and 

 containing various marine excuviae. The depth 

 of the principal bed was nearly twenty feet, and 

 its breadth six or seven. This appears to have 

 been worked at a very remote period, and before 

 iron tools were employed, as large pickaxes of 

 oak, holm, and box, have been found there. 

 In St. Blazey, St. Austell, St. Stephen in Bran- 

 nel, and St. Ewe, are many old stream works 

 which men commonly attributed to Jews. The 

 most considerable stream of tin in Cornwall 

 is that of St. Austell Moor, which is a narrow 

 valley about a furlong wide (in some places some- 

 what wider) running nearly three miles from the 

 town of St. Austell southward to the sea. On 

 each side, and at the head, above St. Austell, are 

 many hills, betwixt which are little valleys, which 

 all discharge their waters and whatever else they 

 receive from the higher grounds into St. Austell 

 Moor, whence it happens that the ground of this 

 moor is adventitious for about three fathoms 

 deep, the shodes and streams from the hills on 

 each side being here collected and caught into 

 floors according to their weight and the suc- 

 cessive dates of their coming thither. The 

 uppermost mat consists of thin layers of earth, 

 clay, and pebbly gravel, about five feet deep. 

 The next stratum is about six feet deep, more 

 stony, the stones pebbly formed, and with a 

 gravelly sand intermixed. These two coverings 

 being removed they find great numbers of tin 

 stones from the bigness of a goose-egg, and larger, 

 down to the size of the finest sand. The tin is in- 

 serted in a stratum of loose, smooth stones, from 

 a foot diameter down to the smallest pebbles. 

 From the present surface of the ground to the 

 solid rock or " karn " is eighteen feet deep at a 

 medium. This stream tin is of the purest kind, 

 and a great part of it, without any other manage- 

 ment than being washed on the spot, brings 

 thirteen parts for twenty at the melting-house.' 3 

 From the shallowness of the stream - tin 

 deposits and the comparative ease with which 

 they could be shovelled out, as contrasted with 

 the difficulties of driving shafts through the rock, 

 it goes without saying that of the two methods 

 the former was the first to be employed. All 

 discoveries of ancient tin mines have been made in 

 diluvial ground, 4 and it may be stated with some 

 degree of certainty that stream tinning prevailed 

 in the early and the mediaeval periods, to the 

 exclusion of lode mining, save possibly when the 

 latter was carried on upon remarkably rich lodes 

 and in shallow depths. 5 A few facts may be cited 

 in support of this statement. The composition 



* Polwhele, Hist, of Cornw. bk. z, p. 10. 



* For an example of this see ' Description of a Stream 

 Work at Drift Moor, near Penzance,' by Jos. Came, 

 Trans. Roy. Geol. Soc. Cornw. iv, 47-56. 



5 Polwhele, Hist, of Cornw. i, Supplement, 64. 



541 



