84 GRAYWACKE. — SANDSTONE. 
particles become very minute, it passes into com- 
mon clay-slate; and when the particles are very 
numerous, and united by a small quantity of cement- 
ary matter, it becomes a sandstone or gritstone ; 
and when the fragments are still larger and angular, 
it is called a breccia; when rounded, pudding-stone. 
What is called old red sandstone by geologists is 
only a species of graywacke coloured red by oxide 
of iron. They may often be observed passing into 
each other, and alternating with mountain lime- 
stone ; it also passes into claystone by losing its 
granular structure. The old red sandstone is so 
called because it is believed to lie lower down, or 
nearer the primitive rocks than another species, 
called the new red sandstone ; but, on the Continent 
of Europe, the old red and coal formations have 
been classed as the upper members of the transi- 
tion series, a method adopted by Dr. Buckland in 
his late Bridgewater Treatise. 
Red sandstone is a rock of considerable impor- 
tance as a building material. When beds of clay 
alternate with this rock, the soil is generally very 
fertile ; but where the sandstone alone prevails, the 
land is mostly barren. A deposite of sandstone 
extends, with few interruptions, from Vermont, 
through Massachusetts and Connecticut, down Con- 
necticut River to Middletown, thence to New-Ha- 
ven, thence to Virginia, a distance of seven hun- 
dred miles.* 
Sandstone contains impressions of plants and 
fish, charred wood, and numerous minerals, such 
as copper and lead, at Simsbury, Conn. ; Belleville, 
Somerville, &c., N. Jersey ; and Perkiomen, Penn., 
&c. In some parts of England the old red sand- 
stone formation is computed to be at least 10,000 
feet thick. 
* Lieut. Mather. 
