622 



SCIENCE. 



[N. S. Vol. II. No. 45. 



Olzewski recently succeeded in produc- 

 ing a momentary liquefaction of hydrogen 

 by allowing it to expand suddenly from 

 140 atmospheres' pressure, when cooled to 

 about — 210°C. with liquid air or oxygen 

 boiling under a pressure of less than 20mm. 

 Its boiling point under atmospheric pressure 

 was found to be — 243. 5°C., only 30° above 

 absolute zero. In a letter to Ramsay (Na- 

 ture, Oct. 3) he now announces that under 

 the same conditions helium shows no sign of 

 liquefaction. Its boiling point is therefore 

 still lower than that of hydrogen, and it is 

 the most volatile substance known. In 

 view of the great difficulty in reaching still 

 lower temperatures, it would seem that the 

 present methods will have to be considerably 

 improved before helium can be liquefied. 



Cassel & Co., London, and Macmillan 

 & Co., New York, will publish shortly: 

 ' Clerk Maxwell and Modern Physics ' by R. 

 T. Glazebrook. Other volumes of the Cen- 

 tury Science Series are: ' Michael Faraday, 

 his Life and Works,' by Sylvanus P. Thomp- 

 son ; 'Humphrey Davy,' by T. E. Thorpe; 

 ' Pasteur, his Life and Work,' by M. Ar- 

 mand Buffer ; ' Charles Darwin and the 

 Origin of Species,' by Edward B. Poulton; 

 and ' Hermann von Helmholtz,' by A. W. 

 Eiicker. 



Macmillan & Co. are about to issue a 

 second edition of Mental Development in the 

 Child and the Race, by Prof. J. Mark Bald- 

 win. The only important alteration is the 

 correction in the tables on page 51 . 



Inasmuch as New Jersey has now been 

 covered by the topographical maps of the 

 Survey, Mr. Henry Gannet has been en- 

 abled to prepare a dictionary of all the 

 names on them and to give references to 

 the particular sheets on which they occur. 

 The dictionary facilitates very much the 

 locating of obscure places, such as villages, 

 brooks, hills, etc., and enables one to 

 quickly acquire a map of any portion of the 



State. The dictionary is published as Bul- 

 letin 18 of the U. S. Geological Survey. 



Mr. Edward Wheeler Parker has ex- 

 tracted from the sixteenth annual report of 

 the Director of the United States Geological 

 Survey his paper on the Production of Coal 

 in 1894. After a brief introduction, de- 

 scriptive of our American coal fields, a re- 

 view of the production and labor statistics 

 follows. A coal-trade review by business 

 centers appears next, and then an account 

 of recent official tests of various coals by 

 the Navy Department. The bulk of the 

 paper is occupied by the review of the sev- 

 eral coal-producing States in alphabetical 

 order. A geographical outline of the pro- 

 ductive fields comes first, followed by sta- 

 tistics alike of output, labor, expenses, acci- 

 dents and similar facts. Although concise, 

 the paper is thorough and maintains the 

 high character that has been established by 

 the volumes on Mineral Resources. 



The Critic states that an interesting col- 

 lection of weapons, ornaments, etc., gath- 

 ered in Africa by the young explorer E. J. 

 Glave, is exhibited at the office of The Cen- 

 tury Co., in whose service Mr. Glave met 

 his death in the Dark Continent, last May. 



It is stated that of 597 trees struck by 

 lightning in the forest near Moscow 302 

 were white poplars ; and farmers are ad- 

 vised to plant these trees as protectors 

 against lightning. 



D. James E. Garretson, dean of the 

 Philadelphia Dental College, and known for 

 his scientific contributions on diseases of 

 the mouth, died on October 27th, at the age 

 of 67 years. 



Mr. Robert Brown, a distinguished bo- 

 tanist and traveller, died in London on 

 October 27th, at the age of 53. Dr. Brown 

 travelled extensively in North America and 

 North Africa, and made important scientific 

 contributions to botany, geology and zo- 

 ology. 



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