530 



SCIENTIFIC NE^A^S. 



[April 6, 18 



For cocoa-nut milk is said to contain both the phosphate 

 and the malate, but not the carbonate of lime. That 

 there may be pearls found in cocoa-nuts, the authors do 

 not presume to deny ; but they are doubtful whether 

 the specimen examined had such an origin. 



As far as naked-eye appearances are concerned, a 

 good specimen of the variety of so-called mammalian 

 pearl is quite undistinguishable from a fine specimen of 

 oriental oyster pearl, from its not only being globular in 

 shape, and of a pure white colour, but from its also 

 possessing the iridescent sheen so characteristic of oriental 

 oyster pearls of fine quality. 



In chemical composition, however, mammalian pearls 

 bear no similarity whatever to pearls found in shell-fish, 

 for they are composed of an organic instead of an inorganic 

 material, namely cholesterin. In minute structure again, 

 they bear a marked resemblance to the crystalline 

 variety of shell-fish pearls. 



As regards the hardness of pearls, again, it may per- 

 haps be as well to remark that really good pearls are 

 very much denser than the majority of persons appear 

 to suppose. This may be judged of from the following 

 facts. 



Being on one occasion desirous to crush into powder a 

 split-pea-sized pearl, Dr.George Harley folded it within two 

 plies of ordinarj' note-paper, lifted up the corner of the car- 

 pet and having placed it on the bare wooden floor stood upon 

 it with all his weight — which is over twelve stone — yet 

 neither that amount of pressure nor the stamping upon it 

 with the heel of his boot sufficed to make the slightest 

 impression on the pearl. It was next given to the 

 servant to break with a hammer ; and when he returned 

 he informed us that on his attempting to fracture it with 

 the hammer against the pantry table, all he succeeded in 

 doing was to make the pearl cut its way through the 

 paper, and sink itself into the wood of the table, as if it 

 had been the top of an ordinary iron nail, and that it 

 was not until he had struck it a hard blow with the 

 hammer against the bottom of a flat-iron that he was 

 able to break it. 



It may be further, perhaps, as well for us to mention 

 that shell-fish pearls are not anything like so easily dis- 

 solved in vinegar as the pretty tale of Cleopatra having 

 taken a large pearl from her ear, and after dissolving it 

 in vinegar drunk it to the health of her lover Antony, 

 would lead one to imagine. For during the course of 

 our experiments we have ascertained that two or three 

 days would not suffice to dissolve, in cold vinegar, a 

 good hard pearl, larger than a garden pea, while hours 

 would be required to extract all the mineral matter from 

 it, were even the vinegar employed in a boiling state. 

 But this is not all ; for after every particle of earthy sub- 

 stance had been dissolved the pearl would still remain 

 of the same bulk, and almost of the identical same appear- 

 ance as before, in consequence of its organic matrix 

 being totally insoluble in vinegar. Hence if the Cleopatra 

 legend is to be believed at all, it requires to be consider- 

 ably modified before it can be made to accord with 

 scientific truth. The only way, indeed, in which the 

 fair lady could have made her pearl disappear by solution 

 at the supper-table, would have been by having 

 it pulverised lay a hard hammer and a strong arm before 

 applying the vinegar to it. For when in a state of im- 

 palpable powder the mineral substance of the pearl would 

 effervesce like a Seidlitz powder — though less strongly — 

 and then when diluted with water be transformed into a 

 refreshing coohng lover's drink ; while the animal 



matter would at the same time be in such a state of 

 fine division as not to be readily appreciable by the eye. 



ROYAL METEOROLOGICAL SOCIETY. 



At the monthly meeting held on the 21st March, the Presi- 

 dent (Dr. Marcet) delivered an address on Atmospheric 

 Electricity. He first alluded to Franklin, who, in his experi- 

 ments in America in 1752, succeeded in obtaining the 

 electricity of a storm-cloud by conducting it along the 

 string of a kite sent into the cloud. De Romas, in 

 Europe, repeated the experiment, and, having placed a 

 wire within the twine his kite was attached to, obtained 

 sparks of nine or ten feet in length. The characters of 

 the two kind of electricities were next described, the 

 vitreous or positive, which was produced by rubbing 

 glass, and the resinous or negative obtained by rubbing 

 seaUng-wax or other resinous substances ; and it was 

 shown, by bringing suspended balls of pith within the 

 influence of these electricities, that electricities of different 

 kinds attract each other, and those of the same kind repel 

 each other. De Saussure's and Volta's electroscopes 

 were next described, pith balls being used in the former 

 and blades of straw in the latter for testing the pressure 

 of electricity. With the object of measuring the force of 

 electricity. Sir W.Thomson's electrometer was mentioned, 

 in which the electricity is collected from the air by means 

 of an insulated cistern letting out water drop by drop, 

 each drop becoming covered with electricity from the 

 atmosphere, which runs into the cistern, where it is 

 stored up, and made to act upon that portion of the in- 

 strument which records its degree or amount. The 

 atmosphere is always more or less electrical, or, in other 

 words, possessed of electrical tension, and this is nearly 

 always positive ; while the earth exhibits electrical 

 characters of a negative kind. The efiects of atmospheric 

 electricity were classed by Dr. Marcet under three 

 heads. — ist. Lightning in thunderstorms. and. The 

 formation of hail. 3rd. The formation of the Aurora 

 borealis and Australis. He explained how clouds ac- 

 quired their electrical activity by remarking that clouds 

 forming in a blue sky, by a local condensation of 

 moisture, became charged with positive electricity from 

 the atmosphere ; while heavy dark clouds rising from 

 below nearer to the earth were filled with terrestrial nega- 

 tive electricity, and the two systems of clouds attracting 

 each other would discharge their electricity, giving rise 

 to flashes of lightning. In some cases a storm-cloud 

 charged with positive electricity would approach the 

 earth, attracting the terrestrial negative electricity, and 

 when within a certain distance shoot out a lightning 

 which would apparently strike the earth ; but it would 

 just as well have struck the cloud, only there was 

 nothing in the cloud to sustain any damage, while on 

 the earth there were many objects lightning would 

 destroy, to say nothing of its effects upon animal life. 

 Thunder is the noise produced by the air rushing in to 

 fill up the vacuum made by the heat of the lightning 

 flash. There may be sheet lightnings, zig-zag or forked 

 lightnings, and globular lightnings. The latter are par- 

 ticularly interesting from their assuming a spherical 

 form. Illustrations were given of objects struck by 

 lightning, the most remarkable being, perhaps, the clothes 

 of a working man, which were torn into shreds while the 

 man himself was not seriously injured. Dr. Marcet next 

 proceeded to show a flash of lightning, which he pro- 



