T92 



SCIENCE. 



[Vol. XI. No. 272 



description, and included all persons of any age who were earning 

 their living : that is to say, all persons engaged in the government 

 service, whether national, state, city, town, or county ; all profes- 

 sional people ; all persons engaged in domestic and personal ser- 

 vice, with the exception of housewives and those who assisted in 

 the housework at home only, and for which they received no stated 

 compensation ; all persons engaged in the various branches of trade, 

 in transportation, agriculture, the fisheries, manufactures, and min- 

 ing ; day-laborers ; apprentices, and those who for various reasons 

 were unemployed for the entire year ; the unemployment being 

 properly classified as regards each occupation in presenting results." 

 The chief purpose of the inquiry was to ascertain, so far as possi- 

 ble, first the depression, if any, in particular trades or industries ; 

 and, second, the extent of unemployment generally, without regard 

 to the particular kind of work performed during the twelve months 

 preceding the taking of the census. 



The main results, as shown in Mr. Wright's summary, are as fol- 

 lows : the whole number of persons, of both sexes, who were un- 

 employed at their principal occupation during some part of the year 

 represented by the twelvemonths which preceded the census enum- 

 eration of population, May i, 1885, was 241,589. Of this number, 

 178,628 were males, and 62,961 were females. As compared with 

 the total population of the State, this shows that for every 8.04 

 persons there was one person unemployed forsome part of the year 

 at his principal occupation ; and as regards sex, that there was for 

 every 5.22 males one male unemployed, and for every 16.03 females 

 one female unemployed, at principal occupation during some portion 

 of the time covered by the investigation. By ' unemployed ' is 

 meant, of course, unemployed at their principal occupation during 

 some part of the twelve months preceding May I, 1885. As a 

 matter of fact, only 822 persons, less than one-third of one per cent, 

 were unemployed during the entire twelve months. Of the unem- 

 ployed, 73.94 per cent were males, and 26.06 per cent females. Of 

 the 822 unemployed during the entire year preceding May i, 1885, 

 91.61 per cent were males, and 8.39 per cent females. More than 

 50 per cent of unemployed were from twenty to thirty-nine years of 

 age. Perhaps the pith of the report is given on p. 266, where it is 

 said, " A little less than one-third of the persons returned as being 

 engaged in remunerative labor were unemployed for about one-third 

 of their working time ; while, on the other hand, the working pop- 

 ulation of the State, considered irv its entirety, were employed at 

 their principal occupation for a little less than eleven months during 

 the census year." The results of the investigation would seem to 

 indicate, Mr. Wright points out, that all the products of manufac- 

 tures could have been secured by steady work for 307 working-days, 

 of 9.04 hours each, if this steady work could have been distributed 

 equally among all the persons engaged in manufactures ; while all 

 the remunerative work of the State, of whatever kind, if it could 

 have been distributed equally among the entire working population, 

 could have been accomplished in 307 working-days, averaging 8.99 

 hours per day. 



The report is extremely valuable, and one more evidence that 

 Colonel Wright is the right man, in the right place. 



Manual for Instruction in Domestic Science. New York, Industrial 

 Education Association, 1888. 



The prefatory note of this little volume states that it is a manual 

 ^' drawn up for the use of the students of the College for the Train- 

 ing of Teachers, and for such teachers as adopt the method of in- 

 struction followed at the college by Miss Julia H. Oakley, professor 

 of domestic economy there. It is not intended to be complete or 

 exhaustive. Its aim is to give the outline of a carefully developed 

 course of instruction in cooking, which shall have an educational 

 rather than a technical value, and to furnish notes for the conduct 

 of the same." All persons who are watching the manual-training 

 movement will admit at once that this manual, and others like it for 

 sewing, industrial art, and wood-working, are absolutely necessary, 

 if crude and empirical methods are to be kept out of the schools. 

 They are as essential as good text-books in arithmetic and gram- 

 mar. This manual is simple and clear, and will be of great assist- 

 ance to teachers. For each lesson an outline is given, and the 

 principles it illustrates carefully developed, before the recipe for 

 its practical illustration is stated. This prevents mere imitation, 



and makes the practical workof the domestic science course rational 

 and educational. The manual will doubtless be widely used, and 

 its influence will be wholly for good. 



Mechanics of Materials. By Irving P. Church. New York, 

 Wiley. 8°. $3. 



The modern tendency in writing text-books upon the relation of 

 forces, and their resistances as manifested upon and in the materi- 

 als employed in engineering, appears to be toward a clearer strati- 

 fication of I he various departments of that l)ranch of science. 



Dynamics and statics have long been clearly defined, but there 

 are many books at this moment before the eyes of students, in which 

 the science of statics and the properties of materials are too pro- 

 miscuously treated to leave a clear impression except upon the in- 

 itiated. The result is, that the average student has but a vague 

 idea of what he has been studying, and of its relation to other 

 branches of science. 



Professor Church's plan of treatment is a threefold division into 

 dynamics, statics, and, to quote his own words, " mechanics of ma- 

 terials : a treatise on the elasticity and strength of beams, columns, 

 arches, etc., for students of engineering." The latter title is that of 

 his latest work, now under discussion. It is a book of 320 pages, 

 and might properly be called a treatise upon molecular mechanics, 

 being a discussion of the laws of resistance to externally applied 

 forces of the molecular fibres of materials when used in various 

 forms. 



The treatment of the subject is independent of the kind of mate- 

 rial — steel, iron, wood, etc. — so far as the development of the for- 

 mula is concerned, as they are based upon certain mechanical 

 assumptions, that are independent of the nature of the material. 



That phase of the subject which will perhaps never submit to 

 pure mathematical analysis — the properties of materials, the be- 

 havior of various kinds of materials under stress, the laws of fatigue, 

 proper working-stresses, etc. — is very properly passed over with 

 an occasional allusion, and such tables of values as may be neces- 

 sary to solve the problems dispersed through the book. 



In this connection it may be said that a table in which the aver- 

 age ultimate tensile strength of soft steel is given at 80,000 pounds, 

 and of wrought iron at 60,000 pounds, without further explanation, 

 is calculated to give the student an erroneous impression of the latest 

 practice, in which even 55,000-pound steel has been recommended 

 for bridge-work, and 80,000-pound steel is considered a high grade 

 to use. 



Again : an allusion to Wohler's law of fatigue of materials as a 

 recent discovery seems a misleading expression to apply to investi- 

 gations made twenty years or more ago. But it is far easier to 

 criticise minor points than it is to improve on the main features of 

 Professor Church's work, an investigation of which discloses the 

 following plan : — 



The first chapter discusses the theory of stress and strain ; and 

 by mathematical investigation, of the action upon an assumed form 

 of elements of the mass, the nature and relation of direct tension or 

 compression, and shear, to each other, are clearly defined. The 

 modulus of elasticity is explained ; and, in short, all the funda- 

 mental principles of stress and strain in the abstract are shown in 

 their true relations. 



Chapters II.-V. inclusive, occupying about one-third of the book, 

 relate to torsion and to flexure of beams. 



The generally employed theories of Xavier have been used in- 

 stead of a more intricate mathematical analysis, and a specially clear 

 statement is made of the assumption upon which the formula; for 

 beams are based. Column formulae are treated in the twenty-three 

 pages comprising Chapter VI. The usual presentation of Euler's, 

 Hodgkinson's, and Gordon's theoretical formula; occurs, and some 

 allusion is made to modifications in practice. 



Consistency, perhaps, prevented Professor Church from giving 

 what students much need, — a clear statement of what our engi- 

 neers are actually doing in practice with the designing of columns, 

 and the fact that certain simple formute derived from experiment 

 seem to agree with actual tests fully as well as, if not better than, 

 those mentioned. 



Chapters VII.-XI. inclusive, taking about one-third of the space, 

 treat of arches mainly by the use of the moment polygon. The in- 



