408 Miscellanies. 
‘The English porcelain is made upon principles entirely different 
from those which govern the manufacture of the French and Ger- 
man porcelain. ‘The paste or biscuit, contains alkaline materials, 
phosphate of lime derived from bones, &c., and is baked at a higher 
temperature than that which is necessary for the enamel, which 
contains lead and not feldspar. The German porcelain is composed 
essentially of kaolin and feldspar ; it is baked at the same time with 
the enamel or glaze, which never contains lead, and is composed es- 
sentially of feldspar.” ‘These two kinds of pottery so very different, 
are usually confounded by professors of chemistry. 
13. Mathematical, Philosophical, and Chemical Instruments.— 
We have received the lithograph circular of Louis and André Bre- 
ton, pupils of the celebrated Lenoir & Fortin. Their establish- 
ment is Rue Servandoni, No. 4, pres St. Sulpice, Paris. 
They pledge themselves to furnish to institutions and individuals, 
all or any of the instruments necessary to science, in all its branches; 
manufactured with accuracy and despatch, and at reasonable prices. 
We invite the attention of the American scientific public to this 
establishment. 
Our miscellany has been unavoidably abridged in the present No. 
to make room for articles, and especially for the abstract from the 
doings of the British Association, which being indeed in themselves 
miscellaneous, in that way it happens that this department is in 
fact more extensive than usual, and we may find it necessary to take 
the same course in the succeeding No. 
