March 14, 1889] 



NA TURE 



459 



I 



which is the terror of the Pamir, would soon have brought 

 it to the ground. At the four corners of the largest of the 

 mausoleums a rude attempt has been made to carve 

 pigeons. At the end of the humbler tombs are some 

 stones sunk in the earth. Some of them have a sort of 

 railing round them, formed of stakes bound together by 

 wooden cords." 



The numerous illustrations are excellent, and the trans- 

 lation is well done, but it is a pity that Mr. Pitman has 

 not given the English names of places. Many readers 

 will not recognize in French forms names which in 

 English forms are perfectly well-known, 



THE TESTING OF MATERIALS OF 

 CONSTRUCTION. 

 The Testi7ig of Materials of Construction. By William 

 Cawthorne Unvvin, F.R.S., M. Inst.C.E. (London: 

 Longmans, Green, and Co., 1888.) 



IN a volume of about 480 pages, Prof. Unwin has con- 

 densed probably all our knowledge of the strength of 

 materials used in construction. The work is unique in its 

 way, there being no other equally trustworthy, as far as we 

 are aware, in existence. 



Engineering structures of to-day are designed with 

 due regard to the strength of their individual parts, and 

 each part is so proportioned that it will safely carry its 

 load, yet not be of greater strength than is necessary for 

 this special purpose. In the Forth Bridge, for example, 

 the strains in each member are calculated to a nicety, 

 and the section of metal is duly proportioned. This 

 could not be done if we did not know exactly the 

 actual strength of the various materials used, as well as 

 their behaviour under varying conditions of load less than 

 the breaking load of the material. It is therefore neces- 

 sary that these data should be obtained by using the most 

 perfect apparatus obtainable, and that the experiments 

 should be made by persons who have given much time 

 and thought to the subject. Bearing this in mind, we 

 gladly welcome Prof. Unwin's work ; his name is well 

 known among engineers as one thoroughly able to write 

 such a work successfully. 



The volume consists of three parts. In the first, the 

 mechanical properties of materials are explained— that 

 is, the phenomena of elasticity and plasticity, and the 



I relations between stress and deformation, so far as they 

 have been scientifically ascertained. In the second, the 

 apparatus used in the engineering laboratory is described- 

 Lastly, the third part contains a collection of the most 

 •complete and trustworthy results of testing of all the 

 CMrdinary materials in use. Chapters IV. to VII. con- 

 tain admirable descriptions of various kinds of testing 

 machines, measuring instruments, and other useful 

 appliances used in an engineering laboratory. These 

 chapters are freely illustrated with excellent woodcuts of 

 .the different instruments, the larger ones of the testing 

 machines being remarkably good. 



The chapters dealing with iron and steel show a large 

 knowledge of their practical working and characteristics. 

 We agree with the author that a standard form for tensile 



I test pieces ought to be accepted by engineers in this 

 country, so that results may be more easily compared. 

 I In all the large steel-works in this country there is now to 



testing the material. This is intended for the makers' own 

 information, and it is also used by the engineers or their 

 assistants under whose specification the steel is being 

 made. Take, for instance, steel plates for the bridge work 

 under the Indian Government specification. Every plate 

 rolled is tested in the following manner in order to guard 

 against the acceptance of brittle or dangerous steel. As 

 each plate is delivered from the rolls, and before it is 

 sheared to dimensions, four samples in duplicate are 

 marked off in the spare material for testing purposes. 

 Tensile test pieces arc taken both lengthwise and across 

 the plate, and similar ones for the quenched bend tests. 

 These test pieces are all stamped with suitable numbers 

 before they are sheared off the plate to be tested. The 

 steel must be of such a strength and quality as to be 

 equal to a tensile strength of between twenty-seven and 

 thirty-one tons per square inch, and to indicate a contrac- 

 tion of the tested area at the point of fracture of not less 

 than 35 per cent. ; the percentage of elongation in a length 

 of 10 inches must be not less than 20. 



The bend test pieces, heated to a low cherry heat, 

 and cooled in water at a temperature of 82° F., must 

 stand bending double round a curve of which the 

 diameter is not more than three times the thickness of 

 the piece tested. If these requirements are not in every 

 case satisfactory, the plate represented by a defective test 

 is rejected ; unless it can be shown that the tested speci- 

 men has surface or other defects, in which case the 

 duplicate test-piece is duly tested to take its place. 



It must be evident, therefore, that a tremendous amount 

 j of testing is now being carried out in this and other 

 countries, and the value of the material, the acceptance 

 or rejection of which depends on the results of the tests, 

 will reach a large amount. On this account we are 

 always glad to increase our knowledge of the behaviour 

 of the material under test, and of the machinery used in 

 the process. 



Prof. Unwin is to be congratulated on having success- 

 fully fulfilled his task. The work is worthy of his reputa- 

 tion, and should find a place in every engineer's library. 



OUR BOOK SHELF. 



Entomology for Beginners. For the Use of Young Folks , 



Fruit-groTvers, Farmers, and Gardeners. By A. S. 



Packard, M.D., Ph.D. Small 8vo, pp. xvi. and 367. 



(New York : Henry Holt and Co., 1888.) 

 Dr. Packard's works on entomological subjects are so 

 well and favourably known, that the book he has now 

 written under the above modest title will certainly obtain 

 a large circulation. 



As its name implies, it is a work especially addressed to 

 beginners in the study of entomology, and gives them a 

 brief outline of the extent of the subject, and descriptions 

 of the various methods pursued in its research. 



In some respects this work is based upon the same 

 author's " Guide to the Study of Insects," many of the 

 paragraphs being the same in both books and also many 

 of the woodcuts which illustrate them. But the portion 

 relating to classification is much abridged in the smaller 

 book, whilst that which treats of the mounting of micro- 

 scopic preparations, &c., is given at much greater length. 

 It is this latter part that will be found of more perman- 

 ent value to the student, who will soon master the brief 

 classification put before him. 



