POPULAR MISCELLANY. 



279 



A Manual of Mechanics. By T. M. Goodeve. 

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Unwise Laws. By Lewis H. Blair. New 

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Scriptures, Hebrew and Christian, arranged and 

 edited for Young Readers. By Edward T. Bartlett 

 and John P. Peters. New York : G. P. Putnam's 

 Sons. Pp. 545. $1.50. 



Eeport of the Smithsonian Institution for 1884. 

 "Washington : Government Printing - Office. Pp. 

 904. 



Class-Book of Geology. By Archibald Geikie. 

 London and New York : Macmillan & Co. Pp. 

 16. $2.60. 



Persia. By James Bassett. New York : Charles 

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Labor, Land, and Law. By William A. Phillips. 

 New York : Charles Scribner's Sons. Pp. 471. 

 $2.50. 



Terminal Facilities for handling Freight of the 

 Railroads entering the Port of New York. By 

 Gratz Mordecai. New York : " Bailroad Gazette." 

 Pp. 68, with Maps. 



The Country Banker. By George Eae. New 

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Triumphant Democracy. By Andrew Carnegie. 

 New York: Charles Scribner's Sons. Pp.519. $2. 



History of the Pacific States of North America. 

 California. Vol. IV. By Hubert Howe Bancroft. 

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Essays on Educational Reformers. By Robert 

 Herbert Quick. Syracuse, N. Y. : C. W. Bardeen. 

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What is Theosophy ? By a Fellow of the Theo- 

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California, from the Conquest in 1846 to the Sec- 

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POPULAR MISCELLANY. 



How the Oyster makes his Shell. Pro- 

 fessor Samuel Lockwood, in a recent lecture 

 before the New York Microscopic Society, 

 answered the question which is asked by 

 the fool in " King Lear " " Canst thou tell 

 how an oyster makes his shell ? " He starts 

 with the hinge-end, at the spot known to 

 conchologists as the umbo. " A small plate, 

 or single scale, now represents each valve, 

 and that is the first season's growth. The 

 next season a new growth, or plate, shoots 

 out from underneath the first one, just as 

 shingles do. The oystermen call these laps, 

 or plates, ' shoots,' and they claim that the 

 number of shoots indicates the years of the 

 oyster. They certainly do contain a record 

 of the seasons, showing the slow-growing 

 and the fast-growing seasons. ... I have 

 likened these shoots to shingles. Now, at 

 the gable of a house the shingles may be 

 seen edgewise. So on the side of an oyster- 

 shell is a series of lines. This is the edge- 

 wise view of the shoots, or season-growths. 



Another factor is the purple spot, or scar, 

 in the interior of the shell. It is the place 

 of attachment of the adductor muscle. Its 

 first place of attachment was close up to 

 the hinge. Had it stayed there until the 

 shell had become adult, how difficult would 

 be the task of pulling the valves together ! 

 the leverage to be overcome would be so 

 great ; for we must bear in mind the fact 

 that at the hinge-end the valves are held by 

 this black ligament, which is, in life, elastic, 

 swelling when the shell opens, and being 

 compressed when the animal draws the 

 valves together. So, with every year's 

 growth, or elongation of the shell, the mol- 

 lusk moves the place of attachment of the 

 muscle onward, that is, in advance farther 

 from the hinge. As it does so, it covers up 

 with white nacre all the scars that are back 

 of the one in actual use as the point of at- 

 tachment of the muscle." To make the 

 similitude of the oyster's shoots, or season- 

 growths, with the shingles on a roof com- 

 plete, "it would be necessary for the bottom 

 shingle on the roof to underlie the whole 

 series, and reach even to the roof-tree, or 

 ridge-pole. Then the second shingle from 

 the gutter must in like manner underlie all 

 the rest of the series ; so of the third, and 

 so on with the rest. In this way lie the 

 shoots, or laps, of the oyster's shell. The 

 last one deposited underlies them all, and 

 every one terminates at the channel in the 

 bill so that this groove in the bill contains 

 a series of transverse lines, each one mark- 

 ing a season, or a year. Thus we get really 

 four factors for the solution of the ques- 

 tion, ' How old is the oyster ? ' all of which 

 are the outcome of the method or way of 

 making the shell." 



The Trap-Dike of Southeastern Penn- 

 sylvania. Professor H. D. Rogers, in his 

 report for 1858 on the geology of Pennsyl- 

 vania, refers to two trap-dikes in the south- 

 eastern part of the State. In the map 

 published in connection with Professor J. 

 P. Lesley's survey, Mr. C. F. Hall connects 

 the two dikes so as to make a single dike 

 about eight miles long. Professor H. Car- 

 vill Lewis, after two years of observations, 

 has found that this dike is only a small part 

 of a long, narrow dike, which passes almost 

 entirely across the southeastern part of 



