252 Identity of Edwardsite with Monazite. 
The discrepancy in specific gravity between the two minerals 
disappears on subjecting larger crystals of Edwardsite to exam- 
ination. I obtained on a fragment weighing 24 grs. the specific 
gravity of 5.00; whereas the Monazite crystal, whose weight is 
3 grs. equals only 4.61. It will no doubt be a difficult point to 
establish an exact agreement between the two, since the speci- 
mens to be examined are not only exceedingly minute, but much 
entangled with other substances, as mica, tin ore, zeschenite, &c. 
After proceeding thus far in the examination, I felt but little 
hesitation in concluding that the analogy would be found to hold 
still further, and extend to an identity in chemical composition ; 
the more so, as I distinctly remembered several ambiguous and 
nearly irreconcilable circumstances in my analysis of Edwardsite. 
All the Edwardsite I could collect by breaking up numerous 
specimens of the rock amounted to but 5.1 grains. In examining 
each fragment in order to separate foreign matters prior to pul- 
verization, I detected one very perfect crystal of zircon, (of the 
form binotriunitaire, fig. 495 of my Treatise,) which taken with 
the fact that they have frequently been observed in proximity to 
the Edwardsite, leads me to attribute in part the zirconia of my 
former analysis to this source. 
My present object was not so much to determine the number 
and proportions of the ingredients as to ascertain whether the 
oxide of lanthanium and thorina are constituents of the mineral. 
It was heated to whiteness for half an hour, with twice its weight 
of anhydrous carbonate of soda. The mixture fused into a hard, 
yellowish gray compact mass, which was treated with — 
water and the insoluble part separated on the filter. 
The alkaline fluid was supersaturated with acetic acid, nr pre- 
cipitated by acetate of lead. The phosphate of lead was ignited 
and weighed 7.5 grs., which is equivalent to 1.38 grs. phosphoric 
acid, or 27.04 per cent. 
The insoluble matter from the aqueous solution of the calcined 
mineral was now treated with nitro-hydrochloric acid, and di- 
gested for several hours. The insoluble portion was separated, 
ignited and weighed. It amounted to 2 grs. Its color was red- 
dish brown. Believing it still to contain oxide of cerium, I sub- 
jected it to a new calcination with carbonate of sodas in order 
to its more complete decomposition. It had the desired effect ; 
for after the digestion of the calcined amass afresh in agua resi 
