146 Dr. Brown on the Nitre, §¢. 
The western part of the island presents moderate eleva . 
tions ; the soil, a good medium of sand and clay, is in general 
fertile ; but a tract near the termination is sandy and barren. 
Some creeks penetrate to near the centre of the island, and 
are bordered by extensive salt meadows. Except the pri- 
mitive range, I have observed in no part of the island large 
beds of rocks that can be called in place ; but rolled masses of 
greenstone, sandstone, gneiss, granite, red jasper, and indu- 
rated clay, appear in general sparingly, but sometimes it 
abundance, on the surface. Lignite has been found in small 
quantities in the western part of the island. A chal ybeate 
spring, of no great strength, is the only mineral water met 
with in Richmond county. The ponds, wells, and streams 
contain a soft water, holding no lime in solution. 
REMARKS. 
We have already published (p. 54.) Mr. Pierce’s dis 
covery of the pulverulent carbonate of magnesia, and have 
pointed out its connexion with Dr. Bruce’s previous discovery 
of the hydrate of magnesia, or pure magnesia jmed with 
water only. Mr. Pierce has now added another important link 
to this chain, and future mineralogists may quote the vicinity 
of New-York as affording, 
1. Pure magnesia, crystallized and combined with water onl 
2, Carbonate of magnesia, pulverulent and white. 
3. Carbonate of magnesia, in very delicate and perfectly 
white acicular crystals. 
We possess specimens of them all. 
3 ——— 
Arr. X. On acurious substance which accompanies the nalivé 
Nitre of Kentucky and of Africa. Communicated in al 
to the Editor, from Samet. Browy, M.D. late of Kentuttt 
now of the Alabama Territory. 
REMARKS. 
Tre scientific public were several years 2g° laid unl 
obligations to Dr. Brawn, for a very interesting and instr? 
