1819.] Scientific Intelligence. 227 
4. From this table it appears, that the length of a degree of 
latitude at the poles is .............4. ... 68°704 English miles 
At lat. 45°... 2... Pe Cc Sori it 69-030 
ment Oe, OPO Fe BS 69:105 
AOE 90 eevee Mad Poasar p He 69-368 
So that the mean Jength and degree of latitude is almost 
exactly 69 miles and +;th of a mile. Of consequence, the com- 
mon estimate of 69 miles and a half to a degree is very erro- 
neous. 
V. Protoxide of Copper. 
About two years ago, I received from Mr. Mushet, of the Mint, 
part of a mass of copper, which had been for a considerable 
time exposed to heat in one of the meltjng furnaces at the Mint, 
of which he has the superintendence. The copper was changed 
into a red, granular, brittle mass, very similar in appearance to 
red copper ore. Grains of copper were interspersed through it 
in very small quantity. On reducing a portion of the specimen 
to powder, and pouring muriatic acid over it in a retort, I very 
speedily obtained a dark coloured opaque solution, quite similar 
to what is obtained when muriatic acid is poured upon a mixture 
of equal weights of fine powdered copper and black oxide of 
copper. This solution is known to consist ef protoxide of cop- 
per dissolved in muriatic acid. When dropped into water, a 
white powder falls, consisting of protohydrate of copper. When 
dropped into a solution of potash, a yellow-coloured precipitate 
falls, which consists of protoxide of copper. The muriatic acid 
solution of Mr. Mushet’s specimen exhibited exactly these 
appearances, and proved to be a pure solution of protoxide of 
copper in muriatic acid. Here then we have an instance of 
copper converted by heat into protoxide. It is the first example 
of the kind which I have yet met with; and on that account 
deserves the particular attention of chemists. All such accidental 
conversions of metals into unusual oxides ought to be cerefully 
recorded. 
I made an analysis of a portion of this curious specimen, 
which is not, however, to be considered as rigidly exact ; for a 
very accurate numerical statement of such a mixture does not 
seem to lead to any very useful consequence. I found the con- 
stituents of 100 gr. of the specimen as. follows : 
meMotipxide of Copper: a <yersie'ais oi» + oisie'nre wreibroieras ws 43°8 
RMBLORIA GOL OME (s:syais ¢xiaize 60s a> lore wbtileve < ate 26-2 
Silica (not quite free from iron and copper). .... 30°0 
100:0 
*,* The mass of copper, above-mentioned, was obtained . 
from the bottom of a furnace used for the melting of copper. ‘ 
The bottom of the furnace is from 9 to 12 inches thick, 
er 2 
