[ 297 ] 
cc had fed in an indigo-field : the indigo had not 
<c only tinged their urine blue, but the cream of 
<c the milk was of a moft beautiful blue colour, and 
et had a radiated appearance from the centre (Is it 
ec not hence probable, that the dye is the oily part 
<£ of the plant?). The milk underneath was clear 
“ and white as ufual.” 
»> 
Dr. Garden wrote, a year ago, that the prickly 
pear grows in great abundance about Carolina ; and 
alfo that the cochineal infedts are found upon it ; 
but hitherto no attempts have been made to cure 
them as the Spaniards do. In hope, that fome rich 
dye may be produced from the plant itfelf, Mr. 
Baker propofed fome experiments to Dr. Garden, 
which he intends to profecute this fummer. 
XXXVII. An Account of an extraordinary 
Shower of black Dujl , that fell in the 
If and of Zetland 20 th October 1 755 *. 
In a Letter from Sir Andrew Mitchell, 
of Wefifhore, Bart . to John Pringle, 
M.D. RR.S. 
SIR, Pall-Mall, June 9th, 1757. 
Read June 23, TN compliance with your defire, I made 
I7j7 ’ JL particular inquiry, whether at or about 
the time the earthquake happened at Lilbon the ifi: 
of November iyyy. any uncommon phenomena 
* See Phil. Tranfadb Vol. xlix. Part 2. p. 509. 
Vol. 50. Qjj 
were 
