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THE POPULAR SCIENCE MONTHLY. 



now used for making the oxides of zirco- 

 nium, lanthanum, caosium, etc., to be em- 

 ployed for manufacturing purposes. A con- 

 siderable number of cases of exceptional dis- 

 coveries of gems of rare value are recorded, 

 but they are so scattered as not to admit of 

 grouping either by kind or place. Among 

 the notable collections of gems in the United 

 States mentioned by the author, are the three 

 hundred and thirty-one antique gems of the 

 late Rev. C. W. King, of England, which 

 have been presented to the Metropolitan 

 Museum of Art ; Mr. Maxville Somerville's 

 collection of fifteen hundred specimens of 

 antique jewel-carving art, now on loan in 

 the Metropolitan Museum ; the Rev. Dr. W. 

 Hayes Ward's three hundred ancient Baby- 

 lonian, Persian, and other cylinders, now 

 the property of the museum ; the gem col- 

 lection bequeathed by Dr. Isaac Lea to his 

 daughter ; and the series of precious stones, 

 including about one thousand specimens, 

 which, though not expensive, are the finest 

 in the United States from an educational 

 point of view, belonging to the National 

 Museum. Mr. Kunz also gives some inter- 

 esting fashion-notes about precious stones. 

 They fluctuate in favor. Amethysts and 

 cameos, much sought for ten years ago, are 

 now thrown out. Rubies, already very high, 

 are all the time rising. Topaz is not in de- 

 mand. Coral is going out, while the popu- 

 larity of amber is increasing. The use of 

 Brazilian pebbles has decupled since 1878. 

 The rare stones known as " fancy stones," 

 which were formerly kept only as specimens, 

 are now looked upon as articles of trade, and 

 us part of the normal jeweler's stock. Mr. 

 Kunz, as agent of Tiffany & Co., had a fine 

 collection of North American precious and 

 ornamental stones at the Paris Exposition, 

 of which we have published a laudatory 

 notice by " La Nature." It included three 

 hundred and eighty-two specimens. 



Botany as a Disciplinary Stndy. Botany 

 is recommended as a disciplinary study by 

 Mr. Gerald McCarthy. It is much in its 

 favor that the objects with which it deals 

 are convenient of access and full of interest. 

 Among the other advantages that it offers 

 are the adaptation of the study of plants to 

 the cultivation of the aesthetic faculties ; to 

 training the mind to habits of close observa- 



tion and discriminating judgment, orderly 

 arrangement, and the "logic of systemiza- 

 tion " ; its presenting the phenomena of life 

 in its least complicated manifestations ; 

 plants offering better opportunities for thor- 

 ough study than is practicable with minerals 

 and animals ; the usefulness of the study as 

 a recreation and mental tonic ; and the inex- 

 haustible field for research which it offers. 

 If some object that the technical names are 

 hard, " at the beginning it will serve just as 

 well to use the common vernacular name, or 

 even invent names for one's self. The name 

 is the least important thing one can learn 

 about a plant, and it is not wise for the be- 

 ginner to exhaust his time and patience in 

 trying to choose the most proper of several 

 possible and equally unintelligible names. 

 Rather he should seek to group the speci- 

 mens around common types, thus learning 

 for himself the philosophy of the natural 

 system." But the scientific name must 

 eventually be learned, and it will come 

 easier after the student has observed well 

 for himself. For young pupils, and older 

 ones who are unfamiliar with Latin, Miss 

 Youmans's " First Book in Botany " is rec- 

 ommended as the best manual to begin with. 

 It will lead up to the more advanced works. 

 But more useful than any book is the stu- 

 dent's field outfit, of lenses and knives, 

 needles and trowel, and air-tight specimen- 

 box. 



Canses of Cn healthiness in Large Cities. 



The mere age of London, said Dr. G. V. 

 Poor, in a lecture at the Sanitary Institute, 

 was one of the reasons why it became un- 

 wholesome. Roman London was buried 

 deeply among rubbish of all kinds, much 

 of which was putrescible, and therefore a 

 source of danger in the soil. Ancient Lon- 

 don was well placed and magnificently sup- 

 plied with water through the Thames and 

 many smaller streams. All the smaller 

 streams had become disgracefully foul, "and 

 for very shame had been covered over." 

 That mediaeval London was very unhealthy, 

 a perfect fever-den, there could be no doubt. 

 The causes of the enormous mortality lay 

 in the marshy, undrained soil, fouled with 

 refuse of every kind ; in the filthy state 

 of the unpaved city, and a perfectly swin- 

 ish condition of the houses of the lower 



