Royal Society. 457 
made a transverse and longitudinal section of the leaf stalk of a 
vine, and raising up the bark an inch below the leaf, inserted it 
in the section of the leaf stalk ; and thus preserving a communi- 
cation between the bark and leaf, the intermediate part being 
‘ rolled tight with paper, he found that the bark acquired thick- 
ness, and a woody character. He next took the leaf of a potatoe 
and planted it; but although it did not, as he expetted, produce 
tuberous roots, it formed, like cuttings of shrubs previous to their 
striking root, a large round lump, which lived through the win- 
ter, and he is now trying whether it will grow into a perfect 
potatoe. He took a shoot of a vine detached from the stock, 
and immersing a part of its largest leaf in water during a month, 
the smaller leaf not only lived but grew, and acquired thickness: 
this he considers a clear proof that the smaller leaf was nourished 
and augmented only by the food it received from the large one, 
which was partly in water. In addition to these experiments 
Mr. Knight observes, that if trees be deprived of their leaves their 
fruit never ripens ; that evergreens bear fruit at all seasons of the 
year, in winter as well as summer; and that deciduous plants 
only produce their fruit previous to shedding their leaves. The 
common holly is seen with its berries in the midst of winter. 
The quality and quantity of fruit, he seems to think, almost en- 
tirely depend on the nature and quality of the leaves; and hence 
the necessity of gardeners being more cautious in stripping off 
the leaves of fruit trees where they tend to keep the sun off the 
fruit. 
Dr. Holland, F.R.S. communicated an account of a manufae- 
tory of sulphat of magnesia in Monte della Guardia, about five 
miles from Genoa. This mountain, which is at the extremity of 
the Appenines, is about 2000 feet above the level. of the sea, 
and abounds in veins of copper and iron pyrites, and magnesian 
limestone. The original manufactory was confined to sulphat 
of iron and copper; but it was discovered that magnesia was 
very abundant, and that it also could be procured by the same 
process. The process is very simple ; the ore is roasted eight or 
ten days with a wood fire, it is then dissolved in water, and the 
sulphats of iron and copper crystallized; about one per cent. of 
the magnesian lime is added, and sulphat of magnesia is formed, 
which is sold in Italy wider the denomination of sal inglesa. 
The peculiarity in this process is the quantity of magnesian lime 
added ; if it were greater, sulphat of lime would be produced ; if 
less, no sulphat of magnesia would be formed. This manufactory 
is but small, and is situated on the side of the hill, about 1600 
feet above the level of the sea, The ore is dug out of the moun- 
tain in a manner to form a kind of tunnel, but the magnesian 
limestone is very abundant. 
June 
