On the connexion of chemical forces with the polarization of light / Nevil Story Maskelyne.

  • Nevil Story Maskelyne
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: On the connexion of chemical forces with the polarization of light / Nevil Story Maskelyne. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    WEEKLY EVENING MEETING, Friday, April 4. H. R. H. Prince Albert, Vice Patron, in the Chair. ^-^Sir Charles Lyell, / On Impressions of Rain-drops in Ancient and Modern Strata. , Foot-prints of reptiles and birds have been observed on the surface of several ancient strata, accompanied by cracks resulting from the shrinkage of mud during desiccation, and it had been fairly inferred that the rocks bearing these marks must have been formed on a beach, between the level of high and low tide. It might therefore have been presumed that the same combination of circumstances wmuld favour the preservation of impressions left by rain-drops, if any rain had fallen on the surface of the same strata, when in a state of mud or sand. Accordingly, memorials of rain have been met with, and Sir Charles Lyell exhibited specimens of fossil rain and liail-prints, collected by Mr. Redfield of New York, from the New Red Sandstone of triassic age in New Jersey, and others of still older date, obtained by Mr. Richard Brown, from green slabs and sandstones of the Coal Measures of Cape Breton in Nova Scotia. Casts of rain-drops were first recognized in 1828 by Dr. Buckland on the lower surfaces of slabs of quartzose sandstone, found by Mr. Cunningham in the Storeton Hill quarries in Cheshire, where they are accompanied by shrinkage cracks, foot-prints of Cheirotherium, and ripple marks. Mr. Redfield and Sir C. Lyell observed others at Newark in New Jersey in 1841, in red sandstone and shale; and still finer examples have been since met with at Pompton, in the same state, twenty-five miles from New York, by Mr. Redfield. The Lecturer had also an opportunity of observing, in 1842, that a shower of rain had left numerous impressions on the mud-flats exposed at low water, in estuaries communicating with the Bay of Fundy ; and he afterwards obtained a collection of specimens of the hardened mud from Dr. Webster of Kentville, some of which are marked by the drops of a heavy but transient shower which fell on the 21st of July, 1849. The average size of the hemispherical cavities is small, but some of them are no less than half an inch in diameter. Many of them are circular, but in some the longest diameter exceeds the shortest by -^th, or even -|rd. They are surrounded by a small rim of mud, consisting of the matter which has been forcibly expelled from the pit by the falling drop ; and this marginal rim sometimes projects as much above the plane of the stratum, as the bottom of the pit ex-
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