13 



THE POPULAR SCIENCE MONTHLY. 



occasion to depart widely from his present 

 performance. One example his descrip- 

 tion of the Edison steam-dynamo will suf- 

 fice to show the accuracy and lucidity of the 

 definitions of this remarkable dictionary : 



Dynamo-Machine, Edison's Large. This 

 is a machine directly in the piston of an engine, 

 and is composed of four electro-maguets, the 

 pcles, and with pipes for the circulation of air. 

 The machine and Porter & Allen's engines are 

 all built on a cast-iron base, the whole weighing 

 about twenty-two tons. The field-magnets are 

 of cast-iron, and the resistance varies between 

 one and two ohms. The magnets are wound 

 with No. 10 wire, Brown and Sharp gauge. The 

 enormous pole-pieces are of cast-iron, and Edi- 

 son maintains the necessity for using such pole- 

 pieces. The armature consists of a steel shaft 

 six inches in diameter. Mr. Edison and many 

 other electricians claim that a low-resistance 

 machine is the best form. Edison's latest dy- 

 namo-machine has a resistance of one two-thou- 

 sandth of an ohm. Ninety-seven per cent of 

 the electricity out of the machine is available. 



The pamphlet on the storage of elec- 

 tricity has the advantage of the dictionary 

 in that Mr. Greer's work consists in little 

 more than editorial revision. The pamphlet 

 contains a good part of Professor Sylvanus 

 Thompson's excellent lecture before the So- 

 ciety of Arts on the storage of electricity, 

 the advantage of the storage-battery as set 

 forth in the circular of the Brush-Swan 

 Company, and the statement of the value of 

 the Faure battery given in the circular is- 

 sued by the American company controlling 

 this apparatus, together with descriptions 

 of various other storage-batteries, some 

 taken from different technical journals, and 

 some written by Mr. Greer. 



On Prehistoric Trephining and Cranial 

 Amulets. By Robert Fletcher, Act- 

 ing Assistant-Surgeon, United States 

 Army. Washington : Government Print- 

 ing-Office. Pp. 32, with Nine Plates. 



Though published as one of the docu- 

 ments of the Powell Geographical and Geo- 

 logical Survey, the matter of this mono- 

 graph is more European than American, but 

 is susceptible of an American application. 

 Tve author has aimed, starting from Broca's 

 summary of the subject in 1877, to collect 

 the accounts of discoveries of examples of 

 trephining and cranial amulets scattered 

 through the journals of anthropology, not 

 only on account of their interest in them- 

 selves, but also for the sake of the illus- 



tration and guidance they may afford in 

 American research. Numerous curious in- 

 stances of the practice of trephining and 

 the fabrication of amulets are brought to 

 light, and the conclusions are adduced that 

 the large number of perforated crania, ex- 

 hibiting cicatrized edges, establishes the 

 existence of a custom of trephining ; that 

 the operation was performed on both sexes? 

 and generally at an early age ; that it seems 

 (from analogy) to have been for the relief 

 of disease of brain, injury of skull, epilepsy, 

 or convulsions; that it was probably per- 

 formed by scraping, possibly by a scries of 

 punctures ; that posthumous trephining con- 

 sisted in removing fragments of the skull 

 of a person who had undergone surgical 

 trephining, in which each fragment was 

 probably to form an amulet to protect from 

 the same disease or injury for relief of 

 which the operation had been performed ; 

 and that the evidence so far confines the 

 custom to neolithic man on the Continent of 

 Europe. 



The Naval Use of the Dynamo-Machine 

 and Electric Light. By Lieutenant J. 

 B. Murdock, U. S. Navy, U. S. Naval 

 Institute, Annapolis, Md. Pp. 44. 



In this paper, Lieutenant Murdock has 

 collected and compiled from the current sci- 

 entific literature of the day such information 

 bearing on the subject as will enable one to 

 reach a more exact comprehension of the 

 field open for the electric light in modern 

 naval warfare. The applicability of the va- 

 rious machines and apparatuses that have 

 been introduced is discussed, and the modi- 

 fications are considered that may be neces- 

 sary to adapt them to use on shipboard. 



" The Sociologist." A Monthly Journal de- 

 voted to the Increase of Knowledge of 

 the Natural Laws that control Human 

 Happiness. Adair Creek, Knox County, 

 East Tennessee : A. Chavannes & Co. Pp. 

 10. Fifty cents a year. 



The publication of this journal has been 

 undertaken for the love of the cause. The 

 editor has sought for a paper especially de- 

 voted to the study of sociology, and, not find- 

 ing it, has decided to furnish one. Profit is 

 not the especial object of the publishers, 

 but to create a means of communication and 

 a means of exchango of thoughts and opin- 

 ions. 



