Geological OhseYvdiioiJS. 189 



Account ofthe Salt-works near Droitwich, published in the second 

 volume ot" the Geological Transactions. The prevailing rock 

 around Droitwich, says Mr. Horner, is a fine-grained calcareo- 

 argillaceous sandstone of a brownish red colour, whicrh contains 

 beds of a grecnish-grav colour, in which are slender veins of 

 crvstallized gypsum. This sandstone, continues he, is tlie same 

 as that which Mr. Aikin has descrilied as occurring to so great 

 an extent in Shropshire and Staffordshire, and which he con- 

 siders to be tiie old red sandstone of WVrncr. The sandstone 

 which Mr. Horner here describes, answers exactly to tlie de- 

 scription of that which I have mentioned in my former paper, as 

 forming one of the beds of the red ground near Bristol, and is 

 characterized by^ its strongly eflfervescing with acids, and by its 

 being sometimes associated with gvpsum : whereas the old red 

 sandstone, independent of its different geological situation, as 

 Mr. Aikin very justly remarks, does not effervesce with acids, 

 contains spangles of mica, and, as far as I have seen or read, is 

 never accompanied by gvpsum. The occurrence of gypsum 

 and rock-salt in England is, I am convinced, in every instance 

 to be referred to tlie red ground ; even in Scotland, where the 

 old red sandstone is so widely distril>uted, its occurrence with 

 gvpsum is so rare, that Professor Jameson, in his Lectures, if I 

 remember right, only gives two instances of it. Having made 

 these remarks upon Mr. Horner's paper, I (puite with great 

 pleasure some passages from a notice of a paper of his lately 

 lead before the Geological Society, On theStructureof the Quan- 

 tock Miils ", where the red .ground is described to cover tl'.e old 

 red sandstone (in the sameM'av, I apprehend, as I have described 

 in mv former paper), so that the distinction between these two 

 formations is clearly made manifest. "Where the hills of gray 

 wacke (says he) sink down into the lower country, their sides 

 are covered with beds of conglomerate passing into red sand-, 

 stone. These beds appear to consist of the same materials as 

 the gray wacke formation, but decomposed to a considerable de- 

 gree." This conglomerate is merely a common variety of the 

 old red sandstone, and is covered by a red agillaceous sandstone 

 containing a variable proportion of calcareous matter. It is of 

 a fine texture, never contains fragments, is in some places tra- 

 versed by veins of gypsum, and appears to be ib.e same rock as 

 that in which the salt-beds of Gheshire and Droitwich are si- 

 tuated. To this succeed the strata of lyas limestone, which arc 

 sometimes seen distinctly resting on the red gypsum rock. 



Having, as I trust, now shown that many strata have been 

 referred to the red ground, which have not the smallest relation 



' \'i<Jc Tiiom^oii's Aiiiiiilb (or May loli. 



to 



