6; YORKSHIRE. ^113 



obtained in this experiment : it lofl: exa(ftly 

 23 grains in folution ; as 50 : 23 :: 64 : 20i. 

 Therefore the incrcafe of weight in this cafe 

 appears to be wholly owing to the deficiency 

 of air. 



Exp. 2. Cement of Pickerkcg Castle : 

 finer fpecimen of the central tower. 



General appearance that of ftalc lime, rnn? 

 together with water, and baked to a cruft : 

 almoft a pure white : furface rough -, fatw- 

 ing the cells and the unbroken granules of 

 the original lime. — Contexture, more brittle 

 than common chalk ; full of pores ; does 

 not appear to have been much worked at the 

 time of preparation. 



One hundred grains yield in decomposition, 

 twenty-one grains of air. 

 42 grains of whitiih grit, 

 5 grains of fufpendible duft-like particles, 

 Cj6 grains of pure chalk. 



103 grains. 



Obs. The refiduum in this experiment is 

 evidently the powder of free/tone. The par- 

 ticles are fmall, and of irregular figures ; 

 very different in appearance (when magni- 

 VoL. I. I fit>d) 



