400 
TKIC GI50L0GIST. 
manner : — A current of chloride of fiiliciura is brought through a 
tube, termiuating by a glass funnel, the wide opening of which just 
touches the surface of water. The chloride of silieitim is decomposed 
in presence of water, even before it comes in contact with the licpiid, in 
the damp air contained iu the funnel, and hydrophane is deposited upoit 
the sides of the latter, it is translucid when wet, opaque when dry, 
and becomes translucid again whenever it is placed in contact witli water. 
Analyzed, it gave a formation similar to that of resiuite : — 
(S i O'Y, 2 H O 
or, water 11-68; silicic acid, 88-32. 
NOTES AND QUERIES. 
Potato Disease. — " The early re-appearance, tlris season, of the potato disease 
ill the Midland Counties, induces me to call the attention of practical geologists 
to. the subject; for jierhaps I may not eiT in supposing tliat soil exercises great 
influence in tlie developciiient of. the, disease. In the year 1855. when travelling 
from tliis place to Penman Jlawr, I was forcibly struck by t!ie fact, that v.'hilst 
all the potato fields in the district occupied by the varieties of the JJevv Red 
Sandstone, througli which my course lay, exhibited unmistulveable sig-ns of this 
disease, no sooner were the older strata, whether carboniferous or Silurian, 
entered upon, than all the potato crops presented a perfectly healthy 
appearance. , Again, in the autumii of last year, all the potato crojis ia this 
region suftered in a greater or less degree ; whilst, as I was informed 1>y an eye- 
wiiness, hi the carboniferous and other strata of Northumbei'land and Cumber- 
land, the potato crops were wholly free from this disease, although the weather 
in that part of England was so wet and ungenial at the time, that the crops of 
corn .cuflered greatly from excess of moisture. It has occurred to mc as by no 
means improbable, that, by a projier admixture of soil, this serious evil might, in a 
great measure, be suppressed, if not -w-holly eradicated ; and, if agi-icultural 
geologists would, through the medium of the Geologist, furnish reports of the 
districts in which the disease is particularly prevalent, and of those where the 
crcps are healthy, it might lead to very benetici-al results. — K. M. Zoknlin,. 
Kenilwortli, August, 1S58." 
Classification of tiik Ptobeck Bf.ds. — " Sm, — As a student of geology, I have 
been much puzzled willi the classitication of the Purbeck bedsj some authors 
representing them as belonging to the Wealden, others to the Oolite, and some 
again as being a distinct formation. Can you inform me, through your invaluable 
Journal, which is most correct. Also, of the origin of the ])opnlar belief in the 
existence of coal beneath Blackheath, near London. — Vours obediently, N. Z. 
Fossil." — The Purbeck and Wealden deposits are probably contemporaneous with 
certain lower Cretaceous marine bods, which are to be found existing in France 
and Switzerland, and were, therefore, anterior in age to our creens-'nd and clialk, 
though to some extent our lower green.sand intercalates with the Upper Wealden 
beds. The rivers of the Oolitic, Wealden, and early Cretaceous period e\'ident!y 
ran from the same lands, though these were progressively moditied in extent, and 
washed by seas, holding, as ages advanced, successively modified faunas. In 
geological language, therefore, the Purbeck and Wealden indicate a transitional 
period between the .Turassie and the Cretaceous periods, partaking in the animal 
and vegetable characters of each. 
