308 Dr. John T. Plummer on the 



furnish. I do not pretend to say, that the water subjected to 

 experiment derives its earthy matters from our blue or our cliff 

 limestone ; I merely point out the similarity of composition. 



For the purpose of showing the very remarkable difference in 

 the quantity of magnesia obtained by complete evaporation of a 

 given measure of water, from the quantity found in a certain 

 portion of the deposit in a copper tea-kettle, I will compare the 

 analyses of equal portions of the earth thus differently pro- 

 cured. 



Having carefully collected, with the bowl of a silver spoon, a 

 large quantity of the most recently deposited matter from the 

 inside of a tea-kettle, as high up as the deposit was made, I dried 

 it, and weighing 176 grs. well pulverized, I poured pure water 

 upon it, and was surprised to meet with considerable difficulty 

 in making the liquid wet the powder. On adding hydrochloric 

 acid, effervescence followed, and when the solution was ren- 

 dered slightly acid, it was left one or two days to depurate, 

 for I discovered insoluble particles floating about in the liquid, 

 and I suspected them to be vegetable matter. On separating 

 this insoluble portion by filtration, and drying it, it weighed one 

 grain and thirty-three hundredths. Subjecting it to the flame 

 from a blowpipe, it resisted the greatest heat I could raise. From 

 a light brown it became a pale red colored substance, perhaps 

 from the accidental presence of iron. It was not soluble in the 

 mineral acids, hot or cold ; it was not gritty ; with potash it 

 formed a green globule full of air bubbles, but did not appear to 

 be chemically combined with the alkali ; the globule was not 

 wholly soluble in water, and I recovered by elutriation nearly 

 the whole of the original powder. 



The clear liquid treated with oxalate of ammonia, and after- 

 wards with ammonia and phosphate of soda, yielded by the usual 

 processes, one hundred and sixty six grains and three tenths of 

 carbonate of lime, and eight grains and five tenths of carbonate 

 of magnesia. From these experiments I deduce the following 

 tables of comparison : 



Composition of deposit obtained by complete evaporation — 

 100 grs. 



Carbonate of lime, - 98.56 



" magnesia, - - 1.44 



100.00 



