SCIENTIFIC SUMMARY. 435 
those families. We may add that.no one is so well qualified as Mr. Busk 
for such a task. 
Thread Cells in Mollusea. — Dr. Strethill Wright shows that he had 
anticipated this discovery in a paper read before the Royal Physical 
Society of Edinburgh. Such cells were formerly supposed to be only 
found iu the hydroid and helianthoid Polyps and the Medusae. Professor 
Allman afterwards discovered them in a species of Loxodes, a protozoan 
animalcule. Dr. Wright found them in an Annelid Spio Seticornis, and in 
the tentacles of Cydippe, one of the Ctenopliora. Since then he has observed 
them on the very minute tentacles of Alcinoe, another of the Ctenopliora. 
In all these classes of animals the thread cells were developed within the 
ectodermal (or outer) coat of the animal. The type of structure also 
differed in the Protozoon, Hydro-medusa, and Annelid ; and the thread 
cells discovered in Eolis resembled exactly those of the Hydro-medusae in 
their structure. Mr. Alder, the greatest authority on these animals, still 
hesitates to assent to the doctrine, on account of its apparent extreme 
improbability. 
Reiner’s Orthoscopic Eyepiece. — Mr. Ross has brought out an eyepiece 
under the above name, said to possess over the Huyghenian eyepiece the 
advantages of a very much larger field, with more light, and yet without 
any sacrifice of defining quality. With a “Kelner” eyepiece you may 
magnify an Arachnodiscus until it appears equal to a dinner-plate in size, 
and yet be able to see the whole of the object. 
MINERALOGY, METALLURGY, AND MINING. 
MINERALOGY. 
Petroleum. — Amidst the 'fears of the timid, the trade in this liquid 
mineral continues to increase with extraordinary rapidity. According to 
the circular of a Liverpool merchant, although the American oil was 
almost unknown in 1860, a total of 9,000,000 gallons was imported into 
Europe in 1862, and not one disaster happened in connection either with 
its transit or storage which would not equally have occurred to any other 
article of production. Recent advices from Belgium state that the Minister 
of the Interior has just taken occasion expressly to declare that this oil is 
not to be considered as one of the articles of inflammable merchandize 
which must be treated by special regulation as essentially dangerous. It 
is said that a line of steamers are to ply in the ensuing summer between New 
York and a British port, solely for the purpose of conveying it to Europe. A 
new well has recently been opened, which is said to yield 300 barrels per 
day ; but the consumption of the article will be so great as to absorb all 
that can possibly be produced. 
Odour of Precious Stones. — Fournet discovered that many precious stones 
owed their colours to carburets of hydrogen. In 1855 J. Schneider, by 
analysis, confirmed this discovery. In a note recently inserted in Poggen- 
dorff’s Annalen, Schneider calls the attention of mineralogists to the em- 
pyreumatic odour which certain forms of quartz and granite give forth 
