236 



NA TURE 



\yan. 6, i< 



determined, all the principal engineering constants, from the 

 tenacity of wrought-iron to the calorific value of coal, or 

 the efficiency of a steam-engine, or the accuracy of an indi- 

 cator-spring, or the discharge-coefficient of an orifice. He 

 thought that this kind of practical experience could be gained 

 best in an Engineering Laboratory, in connection with some 

 institution where technical instruction was given. He claimed 

 that, in the matter of engineering laboratories, as a branch of 

 technical education, England had really taken the lead, instead 

 of being, as was too often the case in such matters, in the rear. 



After distinguishing between laboratories whose chief function 

 was original investigation or research, and those whose main 

 object was the practical education of young engineers, and after 

 giving an outline of the method of work which he had adopted, 

 he went on to enumerate the principal subjects upon which 

 experiments in an engineering laboratory might be carried out, 

 summarising them thus : — (i) Elasticity and the strength of 

 materials ; (2) the economy, efficiency, and general working of 

 prime movers, and especially of the steam-engine and boiler ; 

 (3) friction ; (4) the accuracy of the apparatus commonly used 

 for experimentation, such as springs, indicators, dynamometers, 

 gauges of various kinds, &c. ; (5) the discharge over weirs and 

 through orifices, and hydraulic experiments in general ; (6) the 

 theory of structures ; (7) the form and efficiency of cutting- 

 tools ; (8) the efficiency of machines, especially of machine- 

 tools and of transmission-gearing ; {9) the action and efficiency 

 of pumps and valves ; (10) the resistance of vessels and of pro- 

 pellers, and experiments in general connected with both. The 

 paper dealt mainly with the three first subjects, the others 

 receiving brief mention only. 



In discussing the best form of testing-machine for laboratory 

 purposes the author described specially the Werder machine, 

 used by Bauschinger and largely elsewhere in engineering 

 laboratories on the Continent, the vertical machine of Mr. J. H. 

 Wicksteed, and the horizontal machine of Messrs. Greenwood 

 and Batley, on Mr. Kirkaldy's principle, used by himself. In- 

 cidentally he described a number of other testing-machines, 

 including the Emery machine at the United States Arsenal 

 at Watertown, Fairbanks' machine, and others. The three 

 machines first named were compared in some detail in respect 

 to their accuracy, mode of applying load, methods of making 

 observations, adaptability for varied experiments, simplicity, 

 and accessibility, and the comparative advantages and dis- 

 advantages of each were discussed, the author preferring, on the 

 whole, the Greenwood type. The method of testing employed 

 by tlie author, with pump, accumulator, and Davy motor, was 

 then described and illustrated. 



Different apparatus for the measurement of minute extensions, 

 compressions, &c. , occurring below the limit of elasticity, were 

 next discussed, the instruments specially mentioned being those 

 of Prof. Unwin, Prof Bauschinger, Mr. Stromeyer, and the 

 author, as representing micrometric, optical, and mechanical 

 exaggeration of strains. Automatic test-recording apparatus 

 was next dealt with. Prof Unwin's, Mr. Wicksteed's, Mr. 

 Ashcroft's, and the author's diagramming machines being men- 

 tioned and illustrated. Automatic diagramming apparatus for 

 elastic strains was next discussed. The paper contained fac- 

 similes of various diagrams, both ordinary and elastic. In con- 

 cluding this section of the paper, brief references were made to 

 machines for transverse tests, torsional tests, shearing tests, 

 cement and wire tests, secular experiments, experiments on 

 repeated loads, &c. 



In discussing the design of an experimental engine for labora- 

 tory purposes, the author first enumerated the principal con- 

 ditions under which such an engine should be capable of 

 working, summarising them thus : — (i) Condensing or non- 

 condensing ; (2) simple or compound ; (3) compound, with 

 cranks at various angles ; (4) with the greatest possible variation 

 of steam-pressnre ; (5) with the greatest possible variation of 

 cut-off and other points in the steam distribution ; (6) with 

 the greatest possible variation of brake-power ; (7) with 

 considerable variation in speed ; (8) with or without 

 throttling ; (9) with or without jackets, and with vary- 

 ing conditions as to their use ; (10) with variation of clearance- 

 spaces; (11) with variation of receiver- volume ; {12) with or 

 without arrangements for intermediate heating ; (13) with varia- 

 tion in the reciprocating masses. He then enumerated the 

 principal quantities which had to be measured during an engine- 

 test, making remarks upon each important point in passing. A 

 list was given of the principal experimental engines in existence. 



including those in London, Birmingham, Leeds, Munich, and 

 Liege. This section was concluded by a description of the 

 arrangement of an experimental boiler. 



Under the head of friction-experiments, the principal points 

 were summarised upon which experiments were required, in 

 order that anything like a complete theory of friction in machines 

 might be worked out. These included the variations of velocity, 

 intensity of pressure, extent of contact, temperature, lubricant, 

 method of lubrication, and nature of rubbing material. Fric- 

 tion-measuring machines, used or proposed by Prof. Thurston, 

 Prof R. H. Smith, Mr. Tower, and himself, were briefly 

 described. The paper concluded with a few remarks on 

 laboratory experiments connected with hydraulic work, the 

 theory of structures, the form and efficiency of cutting-tools, the 

 efficiency of machines and of transmissions, the action and 

 efficiency of pumps and valves, and the resistance of vessels and 

 propellers. 



In an appendix there were added : — (a) Forms used by the 

 author for conducting engine-trials, {b) Notes on the principal 

 engineering laboratories in Europe and in America, with brief 

 accounts of the chief apparatus used in each. 



BIRDS' NESTS AND EGGS^ 



""PHE philosophy of birds' nests and eggs involves questions far 

 -*■ too profound to be settled in an hour's lecture. The 

 extreme partisans of one school regard birds as organic auto- 

 mata. They take a Calvinistic view of bird-life : they assume 

 that the hedg^-sparrow lays a blue egg because, under the stern 

 law of protective selection, every hedge-sparrow's egg that was 

 not blue was tried in the high court of Evolution, under the 

 clause relative to the survival of the fittest, and condemned, a 

 hungry magpie or crow being the executioner. The extreme 

 partisans of the other school take an entirely opposite view. 

 They regard the little hedge-.sparrow, not only as a free agent, 

 but as a highly intelligent one, who lays blue eggs because the 

 inherited experience of many generations has convinced her 

 that, everything considered, blue is the most suitable colour for 

 eggs. 



Perhaps the first generalisation that the egg-collector is likely 

 to make is the fact that birds that breed in holes lay white eggs. 

 The sand-martin and the kingfisher, which lay their eggs at 

 the end of a long burrow in a bank, as well as the owl and the 

 woodpecker, which breed in holes in trees, all lay white eggs. 

 The fact of the eggs being white, and consequently very con- 

 spicuous, may have been the cause, the effect being that only 

 those kingfishers which bred in holes survived in the struggle for 

 existence against the marauding magpie. But the converse 

 argument is equally intelligible. The fact that kingfishers breed 

 in holes may have been the cause, and the whiteness of the eggs 

 the effect ; for why should Nature, who is generally so econo- 

 mical, waste her colouring-matter on an egg which, being 

 incubated in the dark, can never be seen? The fact that many 

 petrels and most puffins, which breed in holes, have traces of 

 spots on their eggs, whilst their relations the auks and the gulls, 

 who lay their eggs in open nests, nearly all lay highly-coloured 

 eggs, suggests the theory that the former birds have compara- 

 tively recently adopted the habit of breeding in holes, and that 

 consequently the colour being no longer of use is gradually 

 fading away. Hence, we assume that the colour of the egg is 

 probably the effect of the nature of the locality in which it is 

 laid. 



The second generalisation which the egg-coUector is likely to 

 make is the fact that so many of these birds which breed in holes 

 are gorgeously coloured, such as kingfishers, parrots, bee-eaters, 

 &c. The question naturally arises, Why is it so ? The advo- 

 cates of protective selection reply. Because their gay plumage 

 made them so conspicuous as they sat upon their nests, that 

 those that did not breed in holes became the victims of the 

 devouring hawk, exactly as the conspicuous white eggs were 

 eaten by the marauding magpie. But the advocates of sexual 

 selection say that all birds are equ.illy vain, and wear as fine 

 clothes as Nature will let them, and that the kingfisher is able 

 to dress as gorgeously as he does because he is prudent enough 

 to breed in a hole safe from the prying eyes of the devouring 

 hawk. The fact that many birds, such as the sand-martin and 



' Abstract of a lecture delivered by Mr. H. Seebohm at the London 

 Institution on December 20, 1886. 



