SCIENTIFIC SUMMARY. 
219 
which act independently without being touched, and which indicate the 
temperature to the twentieth of a degree. 
A Rain of Sand. — A curious shower of sand took place in some parts of 
Italy on February 13 and 14 last, and has been described in the Comptes 
rendus by M. P. Denza. This memo'ir, says the Chemical News , contains 
the account of a very curious phenomenon — viz. rain in the southern 
parts of Italy accompanied by a fall of a fine reddish sand, while, in the 
northern parts of that kingdom, snow fell accompanied by the same sub- 
stance. The sand has been tested, and found identical with that which is 
now and then carried by gales of wind from the African desert, not simply 
into Italy, but even sometimes into Switzerland, where some of it fell, along 
with snow, at Tscappina (Canton des Grisons). This paper contains many 
curious facts relating to a phenomenon which is sometimes observed also on 
the Canary Islands. 
Curious Air-cavities in accidentally -formed artificial Crystals. — Some 
curious facts were brought lately before the Boston Society of Natural His- 
tory by Mr. Thomas Gatfield, who exhibited some bottle-stoppers the cavities 
of which contained water. Mr. Gaffield stated that on the morning of 
September 6, a fire occurred in the glass-cutting establishment of J. M. 
Cook, in Congress Street. On the next morning he visited the ruins of the 
fire to search for any specimens exhibiting the devitrification of glass exposed 
to great and long- continued heat. He found nothing of this kind, but 
instead, in a pile of melted glass and cinders of wood, discovered some 
stopples of glass bottles, cracked on the outside and containing water. 
These stopples were originally made with a cavity containing a partial 
vacuum, as the air must have been enclosed when hot, and when cooled 
must have contracted and filled less space than previously. Mr. Gatfield 
presumed that when the glass stopples were heated red hot by the fire 
around them, the stream of water from the engines coming in contact with 
them produced the cracks through which the water rushed in, in sufficient 
quantity to fill the partial vacuum. The glass was cooled by the water 
within, and the fire extinguished by the water without, and so the glass con- 
tracting to its original size has virtually almost hermetically sealed the 
imprisoned water. Mr. Gaffield thought that these specimens might throw 
some light upon the occurrence of crystals with cavities containing liquids, 
and of mineral goedes lined with crystals. 
An Approach caused by Vibration. — At a recent meeting of the Royal 
Society, Professor Guthrie gave an account of some very curious results of 
experiments with vibrating bodies. He showed that when a card was held 
in a certain position near a vibrating tuning-fork, it was attracted towards it. 
The author concluded that the effect of apparent attraction is due to atmo- 
spheric pressure, and that this pressure is due to undulatory dispersion. He 
suggested that the dispersion of the vibrations which constitute radiant heat 
may cause bodies to approach, being pushed, not pulled. 
A new Thermo-Electric Pile. — A piece of apparatus of the thermo-pile 
character has recently been constructed by MM. Mure and Clamond, and 
has been minutely described in some of the physical journals. It con- 
sists of small bars of lead, or native sulphuret of lead, and of plates of steel. 
The bars are 40 mm. long by 8 mm. thick, and the plates of steel are 55 
