Mr. Riddle on the Double Altitude Problem. 131 
that is, 4°78 per cent, and the quantity of antimony required to 
form the oxide be added to it, the remaining quantity of metal is 
sufficient (slight errors of observation being neglected) to form 
with the sulphur the sulphuret of antimony with 3 atoms of sul- 
phur. It will moreover be found, that the quantity of the oxide 
of antimony is to the quantity of sulphuret as the weight of an 
atom of the first is to the weight of 2 atoms of the second ; so 
that the native kermes consists of 1 atom of oxide of antimony 
and 2 atoms of sulphuret of antimony, or of 
Sulphuret of antimony . . . 69°86 
Oxide of antimony .,... 30°14 
The chemical formula is then Sd +2 85s’, which M. Ber- 
zelius had already assigned for the composition of the native 
kermes. This composition is remarkable, as it offers the only 
example of a native crystallized oxy-sulphuret. 
XXI. On Mr. Burns’s Communications respecting the Double 
Altitude Problem. 
To the Editor of the Philosophical Magazine and Journal. 
Sir, 
CERTAINLY did not intend to notice further the com- 
munications of your correspondent Mr. Burns; but I must 
request you to point out a most singular misquotation which 
he makes from my last letter. I stated that “I noted the mis- 
take in his assumption in italics ;” Mr. B. quotes the remark 
thus, “I noted the assumption in italics.” 
No person acquainted with what has been done on the dou- 
ble altitude problem, will expect any notice to be taken of 
Mr. B’s third and fourth solutions, as there is nothing new 
either in the principles of the solution or the formule employed. 
Your obedient servant, 
Greenwich Hospital, Feb. 18, 1826. E. RipDLe. 
To the Editor of the Philosophical Magazine and Journal. 
Sir, 
Havrine, with a little surprise, noticed a paper in your very 
useful work, No. 329, entitled “ A short Method of finding 
the Latitude at Sea by Double Altitudes and the Time between,” 
by James Burns, B.A., I beg leave to say that, though it 
certainly is a kind of double altitude, which he has investi- 
gated, it is not the problem that generally goes under that 
name, and which is so very puzzling to navigators in general: 
R2 neither 
