358 



boiled turn red, like the shell of a lobster. It will not be inappro- 

 priate to distinguish these nodules of the 8pinatus sandstone by- 

 naming them " The Entomostraca Nodules of the Spinatus Zone." 

 The careful examination of the lithology being all important, 

 the mode employed in our case was as follows : first an 

 examination in the dry way was effected. A small portion of 

 the sandstone was cautiously reduced to powder, without 

 crushing the particles composing it ; the powdered substance 

 was next passed through gauze sieves of different fineness of 

 mesh, and thus were the constituents of the rock properly- 

 separated and prepared for examination with the lens. 



A very- correct diagnosis of a rock may thus be obtained. In 

 this instance the result that was ascertained was briefly this : that 

 the main basis of the sandstone was a yellowish calcareous mud 

 of fine composition, with a few siliceous particles of diatomacean 

 orio-in, that would barely impart a polish to a metal surface ; 

 whilst, on the contrary, the remaining constituent in order of 

 coarseness proved to be grains of hyaline quartz, that had 

 sufficient cut from angular surfaces to attack and speedily 

 polish iron or steel. These marly sands may be referred to 

 the same class as the Bridgwater bay sands (West Somerset), 

 of which the scouring bricks known as Bath bricks are 

 composed. Therefore as it is a pleasing office to the geologist, 

 to suggest an economic use for such substances afforded by the 

 earth, yet rejected as effete and worthless by mankind, I would 

 recommend the use of these sands of the Spinatus Zone as a 

 good scouring material. To the farmer, they would prove an 

 excellent dressing stimulus to old worn out clay soils, improving 

 their impervious character, and reviving their fertility by the 

 accession of such fertilizing matter, as phosphoric acid, lime, 

 and finely divided silex, all ingredients grateful to vegetation. 

 The chief drawback being that like the iron ores of our Middle 

 Lias, there exists no considerable quantity of it, and besides, on 

 the top of a hiJl, it is difficult of access. Throughout the whole 

 of the Spinatus sandstone, which corresponds to the "Iron series" 

 of the Yorkshire Lias, the ferric oxide is freely distributed in 

 stains, veins, and lumps. The larger quantity of iron deposit 



