278 An Essay on Rents. [April, 



The foregoing description of the first-formed tabular masses, and 

 their mode of arrangement, is of a general application : but many 

 modifying circumstances are to be taiken into the question in giving 

 an account of all the variations in their arrangement ; but a de- 

 scription of them would be too long for this essay. 



Of the Second-Formed Earthy -Tabular Masses. 



The second-formed tabular masses are known by the names of 

 sticking, dowk, flookans, &c. These masses always resemble the 

 softer ])arts of the matter contiguous t6 the bended-tabular rents ; 

 and consist chiefly of that part of it which is the easiest suspended 

 mechanically in water. They, therefore, generally contain a large 

 portion of clay. In the coal formation they resemble slate-clay, 

 alum-slate, &c. ; but in general they are much softer, and some- 

 times have the consistence of common clay. I have never met 

 with them in liine-stone but in Derbyshire, and there they have 

 proceeded from the slate-clay which lies on the lime-stone. In 

 granite, gneis, and sienite, they consist of soft, greyish, greenish, 

 or yellowish-white clayey matter, just as the colour of the felspar of 

 these rocks may vary. In serpentine they sometimes constitute the 

 substance called soap- rockv In Cornwall they are called flookans; 

 and Price describes a flookan, in his Mineralogia Cornubiensis, 

 " as a tenacious and glutinous earth or clay, that sometimes runs 

 withoutside some veins, immediately between either wall of the 

 lode and the lode itself, and more frequently adhering to the hang- 

 ing or superior .wall, and sometimes mixed in and throughout the 

 lode itself." 



The second-formed tabular masses are generally situated between 

 the upper side of the rent and the first-formed tabular masses, and 

 sometimes between these masses and the lower side of the rent. 

 They lie parallel and close to the sides, and never stretcii across the 

 rent, like the first-formed tabular masses, except when they change 

 from one side to another, which is very seldom. The unshaded 

 parts a, b, c, d, e, fig. 3, represent these masses. They do not 

 continue the whole length of a rent, but are frequently interrupted 

 by the first-formed masses, and by the closing of the sides of a rent. 

 Hence the spaces in the rents which contain these masses are of 

 tabular shapes, which are of various figures and dimensions, 'iliese 

 spaces are generally connected together by channels, which are 

 sometimes very small. But although the greatest part of the 

 matter is arranged in tabular masses which lie near the sides of 

 these rents, yet the rest has adapted itself to every inequality in tiie 

 surfaces of the first-formed tabular masses, and to those in the sides 

 of the rents 3 and has also completely filled every cavity in the first- 

 formed masses, and in the matter contiguous to the, rents, to which 

 they could gain access. 



As the nature and position of the second-formed are so different 

 to those of the first-formed tabular masses, these masses could not 

 both acquire their situations at the same time ; hut as the former 



