Correspondence of J. Nickleés. 117 
sinking through the sandstone, in the expectation of meeting a 
continuation of his crevice in the Lower Magnesian, than he 
e in commencing a shaft anywhere at random in this 
rock, without regard to surface-indication, and expecting to strike 
a valuable lode. He might possibly find one; but the chances 
would be more than ten-thousand to one that he would not.” 
That the amount of lead produced in the Upper Mississippi 
region is gradually diminiekinge is evident from the statistics ; 
the maximum produce of these mines was in the years 1845-47 
When it was nearly 25,000 tons per annum. At present it 
amounts to less than half that. In answer to the question, what 
can be done to develop the mining interest of this region, a sys 
tematic topographical and mining survey of the whole lead-bear- 
ing region is urged as an indispensable preliminary to future suc- 
cessful explorations. A more or less symmetrical disposition of 
the crevices will be found to prevail, and from the symmetry of 
the known, the position of the unknown may possibly be ascer- 
tained. There is no doubt that heavy bodies of ore yet remain 
concealed under the thick covering of drift, which makes surface 
explorations so expensive, and that a large amount of labor is 
wasted in fruitless search for workable lodes which might be 
more profitably expended if more systematically directed. __ 
€ existence of zinc ore in sufficient quantity and under suit- 
able conditions with reference to fuel, labor, and a market, is 
Pronounced highly questionable. Gold is not to be looked for, 
except in the most minute quantity, a caution inserted with spe- 
ar gel 
Specimens of considerable size may, ibly, have found their 
Way out of the pockets of returned California miners, into the 
soil of Iowa. 
In closing the Report, we would express our earnest hope that 
the survey so well begun, may be continued to its completion, 
and that other volumes as valuable may soon follow, 
—————— 
Arr. XVI.—Correspondence of Prof. Jerome Nickles, dated Paris, 
October 26th, 1858. 
80 beyond the bounds of France across the Rhine. We need make no 
xy tor this, as science is of all countries, and the announcement of 
pet news is our special duty as correspondent of the American 
tal. 
