6so 



NATURE 



[October 22, 1908 



on the Ceylon pearl oyster. These dealt with (i) the kind 

 of ground on which the oysters live and the objects to 

 which they are attached ; (2) the oyster-eating fishes and 

 other enemies which affect the life of the oyster ; and (3) 

 tlie different types of oyster and the question of their 

 constancy. 



Dr. A. Smith Woodward gave a lecture on the evolu- 

 tion of fishes. Prof. R. J. Anderson gave details re- 

 specting (i) the epiphyses of long bones, chiefly in 

 sauropsids, and (2) measurements of the maxilla in 

 Mammalia. Prof. Alexander Fraser directed attention to 

 some points connected with the alimentary canal of the 

 higher mammals, and Dr. H. E. Roaf gave a summary 

 of his experiments on the physiological action of the 

 digestive enzymes of certain invertebrates, but these com- 

 munications cannot be summarised in the space here avail- 

 able. J. H. ASHWORTH. 



ENGINEERING AT THE BRITISH 

 ASSOCIATION. 



T' 



'HE president of the section of engineering, Mr. Dugald 

 Clerk, is so well known for his researches on the 

 gas engine, and has done so much to place the theory 

 of gas-engine work upon a true scientific basis, that it 

 was only to be expected that the work of Section G should 

 be largely concerned with gas-engine practice and allied 

 industries. The president in his address gave an instruc- 

 tive and valuable summary of the early history of the 

 study of thermodynamics, and of the application of its 

 principles to engine design. 



After the presidential address on Thursday, September 3, 

 only one paper was dealt with, that by Mr. G. Stoney, on 

 recent developments in steam turbines. At the York meet- 

 ing in 1906 Mr. Stoney read a paper on the same subject, 

 and the present paper, which was a continuation of the 

 former, showed conclusively how rapid the progress had 

 been during the past two years. The author first dealt 

 with the changes in the design of continuous-current 

 dynamos to adapt them to the high speed of the turbine, 

 and stated that now as much as 1500 kw. was put into 

 a single armature. In turbo-blowers for blast-furnace 

 work there had been a great advance ; a blower to deliver 

 20,000 cubic feet of air per minute only weighed 25 tons, 

 against 450 tons for the ordinary reciprocating engine 

 of the same capacity. The use of the exhaust steam from 

 non-condensing reciprocating steam engines in turbines, 

 which took in their steam at atmospheric pressure and 

 exhausted it into condensers, was then dealt with, and 

 such refinements as mixed-pressure turbines, where a high- 

 pressure turbine using boiler steam comes automatically 

 into action when the low-pressure steam supply fails. 

 Improvements in condensers to increase the available 

 vacuum — such a very important matter in turbine economy 

 — were then touched upon, and, finally, the wonderful 

 advance in the application of the turbine to marine work 

 was briefly discussed — in eight years the horse-power so 

 utilised had increased from 25,000 to 1,750,000. 



Friday, September 4, was entirely devoted to a joint 

 discussion with Sections A and B of the first report pre- 

 sented by the committee of the section on gaseous ex- 

 plosions, which was appointed at the Leicester meeting 

 in 1907. This report not only summarised in a convenient 

 form for reference what was known up to the present 

 time on the subject, but also described the experimental 

 work which had been carried out by various members of 

 the committee. While Boyle's law' might be considered 

 holding under all the conditions met 'with in gaseous 

 explosions in the gas engine, it had long been realised 

 that it was probable that the law PV = /,'T did not hold 

 at the high temperatures reached in such exolosions. The 

 experimental work on this question was divided in the 

 report into three classes : — (a) constant-pressure experi- 

 ments; ^(6) constant-volume experiments; and (c) experi- 

 ments in which both volume and pressure were varied ; 

 those carried out by Mr. Dugald Clerk fell into this last 

 class. The results obtained bv the various experimenters 

 were fully discussed in the report, and from data obtained 

 from several of the best-known experiments curves were 

 drawn showing the relation between the temperature in 

 NO. 2034, VOL. 78] 



degrees centigrade and the energy in calories per gram 

 molecule. As a result of its investigations the com- 

 mittee had prepared a table giving the energy at four 

 different temperatures in calories per gram molecule of 

 air, CO,, H,0, gas-engine mixture, and ideal gas, and 

 curves were drawn for the gas-engine mixture and the 

 ideal gas. In the form of an appendix to the report was 

 a valuable note, by Prof. H. L. Callendar, on the devia- 

 tion of actual gases from the ideal state, and on experi- 

 mental errors in the determination of their specific heats. 

 Prof. Callendar showed that there was a possible systematic 

 error inseparable from experiments made by Regnault's 

 methods, due to the fact that the correction required for 

 the flow of heat by conduction from the heater to the 

 calorimeter had to be based upon experiments made with 

 no gas passing. A long and interesting discussion took 

 place, the chief speakers being Dr. Marker, Prof. Harold 

 Dixon, who has done such excellent work in the deter- 

 mination of the specific heats of gases at high tempera- 

 tures. Prof. Dalby, Prof. Colver, who described the method 

 by which he had determined the fluctuation of tempera- 

 ture on the inner surface of the cylinder wall of a gas 

 engine, and Prof. Bernard Hopkinson, who stated that 

 in his experimental work he had discovered that the gases 

 at the moment of combustion were able to radiate a con- 

 siderable quantity of heat. The discussion was closed by 

 the president of Section G, who expressed the view that 

 the experimental work which is now being carried out by 

 Prof. Callendar and Prof. Dalbv, which was referred to 

 by the latter gentleman in the discussion, would be of very 

 great importance. Prof. Callendar and Prof. Dalby in 

 their experiments on the determination of temperatures 

 inside gas-engine cylinders used an extremely fine platinum 

 wire, and withdrew it from the cylinder during the time 

 the temperature was at its maximum, and, as a result 

 of their work, they believed they had obtained tempera- 

 tures accurate to within 1° C. ; if the temperature is 

 known accurately at one point of the indicator card, it 

 could certainly be calculated for other points. 



On Monday, September 7, the first three papers were 

 devoted to peat and producer gas. Captain Sankey read 

 the first paper, on the utilisation of peat for the making 

 of gas or charcoal. He stated that the subject was one 

 of great importance to Ireland, and was of interest in 

 view of tlie fact that a Bill had been passed by Parlia- 

 ment sanctioning works to produce gas from peat, and to 

 use this gas for making electricity by means of gas 

 engines and dynamos, and to distribute the power thus 

 generated to works which would be established in the 

 neighbourhood of the power station. The Bill had given 

 power to utilise a portion of the bog of Allan, near 

 Robertstown, on the Grand Canal, about twenty-five miles 

 from Dublin. Earlier attempts to utilise peat had failed, 

 because they were based on the use of dry peat, that is, 

 peat containing 25 per cent, of water, and the cost of 

 such drying and of converting the dry material into 

 briquettes was too great to allow it to compete with coal, 

 and, further, there was no recovery of by-products. The 

 proposed scheme proceeded on different lines ; the peat 

 would only be partially dried, that is, to about 60 per 

 cent., and it would then be used in producers for 

 generating gas, and the by-products would be recovered. 

 It was hoped that the profits on these would cover the 

 cost of procuring and drying the peat. Great progress 

 had been made in Germany in the utilisation of peat, and 

 the author described several plants he had seen at work. 

 The peat could be obtained by four different methods : — 

 by hand labour entirely, by cutting by hand and then 

 shovelling it into an elevator, or by digging it and spread- 

 ing It for drying by a machine, or, finally, the peat could 

 be dug by means of an ordinary grab, which was the 

 method adopted at Schelecken, in Prussia. Probably the 

 grab method would be the best for the proposed power 

 scheme, and the drying might be carried out by means 

 of Dornberg presses. The principal by-product in the 

 manufacture of peat gas is sulphate of ammonia, and 

 the proposed power station would probably be able to 

 produce about 3000 tons per annum. Other important 

 by-products are acetate of lime, methyl alcohol, and tar ; 

 an excellent waggon grease can be made from this tar. 

 The author estimated that the monetary value of these 



