STRANGWAYS : HARROGATE WELLS. 
321 
The Yoredale rocks at Harrogate, consist in the upper part of 
dark blue shales, these being- succeeded by thin bands of earthy 
limestone and chert containing- Encrinites. This cherty limestone 
is the so-called roadstone of Harrogate ; its exact position in the 
geological scale is somewhat doubtful, Prof. Phillips considering it 
to be the equivalent of the main or twelve fathom limestone at the 
top of the Yoredale series.* It is a hard siliceous rock with a con- 
choidal and hackly fracture, but it is very frequently much 
decomposed, having all the calcareous portion dissolved out, when it 
resembles pumice-stone in texture. It is extensively quarried in 
the neighbourhood for mending roads. These cherty beds rest on 
dark blue shales containing sulphur, iron, and probably several other 
chemical substances ; and below these again, we have a thin rubbly 
sandstone also containing sulphur and iron, resting on other beds of 
shale, which are the lowest strata visible in the neighbourhood. 
The precise equivalents of these measures to the west, are 
rendered somewhat doubtful by the thinning out of one or more of 
the beds in the country to the west of Harrogate ; for if we 
examine the country west of the Millstone Grit area, where we 
should expect to find the same measures cropping up, we can discover 
no rocks which exactly correspond to those at Harrogate. The 
reason of this is, either that the Yoredale measures gradually become 
thinner until they finally disappear in their passage to the west, or 
that they are so altered in their general composition, as to be no longer 
recognisable as the same beds. When such changes as these take 
place in an isolated area like Harrogate, it is extremely difficult to 
identify the beds, or to say exactly to what part of a formation they 
belong. In this case, the only clue we have to their correlation 
with the strata of a known area, is the lithological character of the 
rocks, and even this is not always to be depended upon. But we 
shall not be far wrong in considering these beds at Harrogate a 
portion of the Yoredale series, for it is evident they lie below the 
Millstone Grit, while at the same time they must be above the Scar 
Limestone, unless that formation had thinned out, which is not at 
all likely in so short a distance. 
* Quart. Journ. Qeol Soc, Vol. XXL, p. 234. 
