6. YORKSHIRE. in 



I have beflowcd Ibmc attention on the dc- 

 compofitlon of thcfe four fpccimens. The 

 refults are as follow : 



Exp. I. Cement of Pickering Castle : 

 — the ^o^r/^rf[)ecimen, taken from the ruins 

 of the central tcwer. 



In general appea'-ance it refembles dirty- 

 chalk, thickly interfperfed with fmall gravel -, 

 fome of the granules as large as peas. Its 

 tenacity that of common writing-chalk; the 

 afperities eafily broken off with the fingers. 



One hundred grains, pounded, dried, im- 

 merged in v/ater, and balanced together with 

 the menftruum, loft in folution 25 [ grains 

 of air ; and yielded by filtration 40 grains 

 of refiduum ; affording by elutriation 35 

 grains of gravel and rough fand, and 5 grains 

 of fufpendible mud-like matter : the folu- 

 tion yielding by precipitation 64 grains of 

 calcareous earth. 



35 grains 



fome towers raifed hy (I thiiik) Edward VI. Bjt when 

 the parts which are here the fubje£t of notice were 

 erefted, is probably uncertain. They are fuid to be 'af 

 very great antiquity. 



