386 W. P. Trowbridge on Deep Sea Explorations. 
reddens, melts, takes fire and burns with vivid combustion. 
The picrate of protoxyd of mercury is a greenish-yellow, very 
insoluble precipitate. 
_ Picrate of Silver is but slightly soluble. Nitrate of silver poured 
into a solution of a soluble picrate, as picrate of magnesia causes 
at first no precipitate, but after a few minutes beautiful radiating 
clusters of needles form in all directions through the liquid. 
‘crate of Urea.—This very beautiful combination is easily ob- 
tained by dissolving urea in solution of picric acid. It erystal- 
lizes in large fan-shaped aggregations of bright yellow needles, 
Tmanent in the air. 
 Picrate of Quinia.—Alkaline picrates added to solution of sul- 
phate of quinia throw down a bright — powder, insoluble 
in water, but very soluble in alcohol. By spontaneous evapora- 
tion of the alcoholic solution in a beaker glass covered with 
filtering paper, small tufts of yellow needles are obtained. The 
statement of L. L. Bonaparte quoted in Gerhardt (Chemie Organ- 
ique, iv, 123) I have not found confirmed. Heated on platinum 
ou, it burns quietly with a yellow flame. 
Arr. XLIV.—On Deep Sea Explorations; by Prof. W- P.. 
TROWBRIDGE. a 
of the globe, may be compared to the ideas which existe 
minds of men, with regard to the form of the continent of 
ish 
navigators. Previous to the discovery of Columbu 
exaggerated notions were entertained of the boundless extent, 
the unfathomable depths, and the dark wastes of that great chaos 
of waters which no man had yet dared to explore. ~. 
The discovery of the great navigator, was quickly followed 
by the explorations of Ponce de Leon, Cabot, an aes _ : 
d 
tou — various points of the unknown land, an | 
back to the old world trophies from the new. Many of the 
charts made by these bold mariners are still preserved as me 
morialsof their achievements; but what a contrast do they pre 
sent to the maps of the present day; in most of them, scareé 
a resemblance can be traced to the form of the continent wile) 
we now inhabit. The world does not cease to honor these ad 
venturous pilots, because their first efforts were not entirely suc: 
-oessful : imimgeeat researches, with the help of continued im- 
iwi a 
* 
