36 



Ewyas Harold, these quarries not having been opened, I suppose, at the time of 

 the survey. 



Last year, in describing what I called the concretionary Cornstones, I spoke 

 of them as formed entirely of nodules or concretions, not being then aware of the 

 appearances presented in the quarries we have just .inspected, where at the 

 bottom of the bed there is a solid deposit of pure limestone about four feet thick, 

 above which the limestone is found for a depth of six feet in the nodular form, the 

 nodules gradually becoming smaller towards the top. In a quarry which I shall 

 point out to you presently close to Ewyas Harold Castle, the bed of Cornstone 

 about eight feet in thickness, contains two solid strata separated by a layer of 

 nodules. These transitions and alternations seem to indicate a variation in the 

 supply of lime, the soM strata being apparently formed when the water from 

 which the Ume was deposited was nearly free from other minerals, the nodules 

 resulting from such a mixture with earthy matter as to prevent the lime forming a 

 solid stratum. 



Those of you who know anything of the nature of chemical analysis will 

 readily understand that a complete analysis of a mineral substance, can only be 

 performed by those who give special attention to such pursuits, and who have a 

 laboratory at their command. It may be of use, however, to describe a simple 

 mode of ascertaining the amount of earthy impurities present in such limestones 

 aa we have seen to-day. I take a known weight of the specimen to be examined, 

 say 100 grains, and dissolve it in hydrochloric acid ; then filter through a paper 

 filter of known weight, wash the filter until it is free from acid, then dry the filter 

 and weigh it. The increase of weight of the filter gives approximately the 

 amount of earthy impurity in the limestone, this impurity consisting chiefly of 

 silica and alumina, or sand and clay, the deficiency on soluble portion being 

 carbonate of lime, with perhaps a little carbonate of magnesia. In a specimen 

 from the solid bottom bed which I have examined, the insoluble residue amounted 

 to 3'3 per cent., and in a portion of one of the nodules to 6*3 per cent. ; the 

 soluble portion, chiefly carbonate of lime, being in the former case 96 "7, and in 

 the latter 93 "7 per cent. 



The discoveries made on the present occasion were confined to a specimen 

 or two of the egg-packets which have been termed Parka decipiens, and plentiful 

 tracings of a dark substance in the stones which seemed very like carbonaceous 

 matter, but in which Dr. M'Cullough had not yet been able to detect any organic 

 structure with the microscope. 



"St. Martin's well" was next visited— a picturesque well of excellent 

 water, and a high renown for its virtues in restoring weak eyesight ; and then 

 under the guidance of the Kev. W. R. Lawrence the descent to the village was 

 made. Here the church was kindly thrown open, and its restoration fully 

 appreciated by those who chanced to visit it with the Archaeologists two years since. 



