Prof. Horsford on the Rocks of the Florida Reefs. 247 
The total loss by —e ignition included organic ey 
water as hydrate of lime and.carbonic acid, was as follows 
I. 2°7875 gr. lost 1-2687 gr. If. 05910 gr. Jost 02600 er. 
The water was determined in a chlorid of calcium tube, with 
the aid of a low red-heat-and an aspirator. (A heat of 175° C. 
in an oil bath, expelled but a very small proportion of the water.) 
I. 0:7519 gr. lost 0-0259 gr. If. 1-2890 gr. lost 0:0280 gr. 
The organic matter was determined by washing on a dried 
filter the hydrochlori¢ acid residue. . 
I 1-7181 gr. gave 00028 gr. II. 0:4461 gr. gave 0:0021 gr, 
_ The carbonic acid was determined in an evolution flask glass. 
The results with different specimens varied greatly, and are far 
from being satisfactory. 
I 0-8605 gr. lost 03347 gr. —s‘TL.-«(0-1720 gr. lost 0-0585 gr. 
Il. 0:1745 gr. lost 0-0600 gr. IV.  1-6116 gr. lost 0-6277 gr. 
The lime was precipitated a8 oxalate and weighed as carbonate. 
I, 13248 gr. gave 12581 gr. ‘TL. (02550 gr. gave 02330 gr. 
The silica was determined in the usual way. 
Ll. 13245 gr. gave 00002 gr. IL 0:3760gr. gave 0-0005 gr. 
The chlorine of the chlorid of sodium was determined as chlorid 
of silver. ; 
I. 0:8933 gr. gave 0-0303 er. ‘II. 0-6850 gr. gave 0-0101 gr. 
Expressed in per cents. we have :— Dei $ 
| won Matter from - 43-99p.c. to A551 p.c. 
Wate a ele 1 a 
Oran: Matter “ - 0-16 ms Hes 
Carbonic Acid  “ - ; ond * ; 98.94 
Lime On BERT: beri 
Chilorid of Sodium * ee “« 0-04 
Silica < 0-01 “« 60-01 
It is conceivable that the variability in the carbonic acid and 
water, wc due to the more or less advanced stages of change which 
th k has undergone. In the ultimate form of limestone all 
"the veal a as hydrate in the earlier stages, will have be- 
come carbon 
Se i dient permit no action like that occurring in 
“@raulie-cements, . which silica plays an important part ; or lik 
that presented in the hardening of gypsum, in which caielicnis 
acid is n 'y- “To one of be two remaining processes, if to 
either, must it be aseribed ; and as hydrate of lime is present, it 
cannot be Steals eth toa ze with calcareous spring 
