206 THE PERMIAN FORMATION. 



oarbonated, alkaline,, and ferruginous springs, which doubtless, then as 

 dow, broke forth in considerable numbers on the Millstone Grit and 

 Yoredale borders of the Yorkshire area, the coal measure country of 



Yorkshire and Derbyshire, ami the Carl iferous Limestone hills 



beyond, would carry down in solution and in quantities practically 

 without limit, all the mineral ingredients necessary for the production 

 of dolomitic Limestone, Gypsum, and (?) Rock Salt, as also of the iron 

 oompounds thai are found in the Permian rocks of the district. («) 

 Some time would elapse before a state of saturation high enough to 

 cause precipitation was reached. At first then, only mechanical 

 d. 'posits would be formed. These are the "Quicksands." After a 

 time the waters woidd become sufficient^ saturated to cause dolomitic 

 mati nals to ho thrown down to some (Mont, which commingled with 

 jand and mud. as also with the large supplies of ferrous 

 ite (undecomposed in the presence of so much decaying 

 i liki wise brought down by the rivers, would give rise 

 to the blue col Hired plant bearing dolomitic sandstones and shales of 

 : Mar] Slat.' Beries. During this stage mechanical deposition 

 predominated, on the whole over chemical precipitation ; but mi ro- 

 se, ,pic ami chemical examination alike show that some of the beds 

 are true Dolomites, (See Plate IX. ,i while others appear (from their 

 brisk effervescence with an acid) to be non-dolomitic Limestones. 

 Subsidence went on chiefly in the South, or rather South-eastern 

 parts of the known portion of the above Permian area, for it is in 

 that direction that we find these Marl Slates gradually thicken out. 

 Plan! life appi are to bave flourished abundantly, and in some variety 

 on the adjacent land ; the aquatic fauna, bowever, appears to bave b< i d 

 extremelj limited, only a very few bivalve molluscs, and the tracks 

 of annelids, in addition to the ganoid fishes, baving been found in these 

 Somewhat suddenly but without the slightest discernible 

 physical disturbance this state of things came to an end. Chemical 

 precipitation now began to predominate over mechanical deposition. 

 and the formation of the white and yellovi Dolomites of the Magnesian 

 Limestone Stage commenced. Some special explanation is, I 



think, ae ded o a ic t for this sudden change I would explain it 



by supposing the climate to ha, warmer. (6) As a result of 



i summer' i ire would be greater evaporation, and. 



consequently, greater precipitation of mineral matters. The rainfall 



also mighl be thus lessened, so thai the rivers would carrj down less 



bo mineral sprim.-. produced by volcanic 



to turn is) i the mineral Baits of lime and magnesia, as also of iron which 



• • ii I hi in in nth in the Magnesian Limesto rth-«ast of England. 



But thei ■ mic activity in this dist id m Permia a 



i all;, no nei i l11 back on such an hypothi is. n 



stone Grit aloi urnish iron enough ; the whole system is replete with 



Iron, in the fo m ol bisulphide and carbonate, Ail over its surface new. 



i. mit copiously charged with iron. The Carboniferous 



Limestone ii magnesia: ordinary mineral springs will supply 



tiic lesia. 



in dry and ons with closed I i basins," says 



r>r. T. Bterry Hunt, "thai we must the production ol Magi 



cit, 



