18 FORMATION OF THE SOCIETY : UNPUBLISHED RECORDS. 
given seams at places distant, say a few hundred 5\ards, thus we may 
perhaps account for a sandstone gTadually passing into a shale, or 
vice versa. 
There are several disputed points in the Yorkshire Coal-field, 
the most material question for decision is as to the identity between 
the Middleton Strata and those containing the Lofthouse or Haigh 
Moor Coal, and particularly whether the Middleton Main Coal is the 
same as the Lofthouse Coal, and the Lofthouse the same as the Haigh 
Moor. Till a short time ago the universal opinion was that they are 
the same but altered in appearance only by Dykes. However, from 
some circumstances observed lately some think, and indeed with 
sufficient reason, that they are quite dissimilar, and the Lofthouse or 
Haigh Moor strata mil eventually be found to be superior to the 
Middleton strata — this point I have hopes will be investigated at our 
September meeting. Respecting the Dykes it would be material to 
observe whether they are, as is generally supposed, chiefly do^vncasts 
to the South or S.W ; how the inclination of the strata is affected on 
each side, and whether a large Dyke is always accompanied by a 
smaller one running parallel with it, but its heave being opposite to 
the large one, several instances of this I have noticed. I would 
here too remark that the " Cleet " is very indistinct in the vicinity of 
Dykes, and in some cases totally obliterated. As to a test for the 
quality of the air in a colliery which at present is judged of by the 
colour of the exterior of the flame of the candle, when the blue is so 
intense as that of burning sulphur we consider it very dangerous, and 
comparative safety depends on the shadow between that blue tint and 
the brown or yello^nsh tint observed when a candle is burning in the open 
air. So much, howevei', depends upon the quality and nature of the 
material of which the candle is composed that different results may 
be obtained in the same air by using wax candles or tallow candles, 
and again, separate results may be observed with tallow candles 
which have cotton and tow wicks, but besides all this the particular 
shade at which danger commences with each description of candles 
has to be carried in the eye, at best a had memory to trust to. 
It has often occurred to me that an instrument might be contrived, 
which by showing the specific gravity of the air would at once at a 
