November 23, 191 1] 



NATURE 



123^ 



until — in certain alloys— it falls below the ordinary atmo- 

 spheric pressure, and oxidation as well as cementation 

 talces place. On the other hand, the addition of a 

 '■ nobler " metal, such as nickel, raises the critical pressure 

 and allows of the use of gases under higher pressures for 

 cementation without risk of spoiling the articles by surface 

 oxidation. Two interesting conclusions are drawn by the 

 authors. The first is that for a given steel there is a 

 limiting pressure for cementation, by means of carbon- 

 carbon-monoxide mixtures, beyond which surface oxidation 

 sets in. The second is that in the case of chromium alloy 

 steels the pressure of CO and COj must be diminished 

 below atmospheric to allow of cementation without oxida- 

 tion. Since it is only the partial pressure of these gases, 

 however, which comes into effect, this diminution below 

 atmospheric pressure can be produced by simple dilution. 

 It follows, and the authors describe an experimental verifi- 

 cation, that in these circumstances oxidation can be 

 avoided by diluting the stream of " cementing " gases (CO 

 and CO,) with air. The oxygen, of qourse, combines 

 with the granulated carbon in the furnace to form CO and 

 COo in the proportions required by the equilibrium con- 

 ditions, while the remaining nitrogen acts as a diluent and 

 produces the desired effect. 



We have here a series of remarkable deductions and 

 experimental verifications of facts which appear almost 

 incredible to any steel-worker not conversant with the 

 theory of physico-chemical equilibria ; indeed, the practical 

 man will probably find it difficult to believe them until he 

 has tried for himself. None the less, there is here a basis 

 for the rational and scientific conduct and control of a 

 process hitherto largely based on " rule of thumb." 



W. ROSENHAIN. 



THE INSTITUTION OF ENGINEERS AND 

 SHIPBUILDERS IN SCOTLAND.' 



'F'HE annual volume of the Transactions of the Institu- 

 tion of Engineers and Shipbuilders in Scotland, which 

 at the close of the session 1908-9 had 1650 members upon 

 its roll, contains several valuable papers. The president, 

 Mr. C. P. Hogg, in his address, after passing in rapid 

 review some of the outstanding developments in engineer- 

 ing during the past 100 years, directed attention to some 

 >f the problems of the future; in his opinion the nineteenth 

 cntury demonstrated how to utilise the forces of nature, 

 while the problem of the twentieth century will be how 

 10 do so efficiently. 



Mr. C. A. Ablett in a paper on electrically driven re- 



ersing rolling mills described in detail the Ilgner system, 



111 which the power, supplied under very economical con- 



'litions by a steam turbine or a gas engine, is applied to 



'Irive a reversing mill. The mill motor is a direct-current 



hunt-wound machine ; interposed between it and the 



iiurce of power supply is a fly-wheel converter set in 



order to provide a system by which the mill motor may 



l>e started, stopped, reversed, and kept under control in 



regard to spcpd without loss of energy, and at the same 



ime to enable a control apparatus of reasonable 



limensions to be employed. The electrical equipment of a 



, 6-inch cogging mill at Osnabriick was described as an 



xample of this system, and the paper was illustrated by 



a series of drawings and photographs of the plant; especial 



attention was given to the flexible coupling between the 



fly-wheel and the electrical machines of the converter set. 



In the discussion on this paper Mr. T. B. Mackenzie 



xprcssed the opinion that German steel makers were able 



n many, cases, owing to their skilful utilisation of waste 



•nergy, to roll their steel at lower rates for power than 



:sually obtained in this country; he believed that in the 



I eel works of the future there would bo no reciprocating 



team engines employed — the whole of the power needed 



would be generated by gas engines in a n-ntral station 



ind distributed electrically to the various mills. 



In a paper by Mr. A. Melville, the " Simplex " method 

 'f concrete pile foundations was described; the essential 



, . ', Tf^nsactions of the Institution of Eneinrers and Shipl)uilders in Scotland. 

 \ ol liii. Fifty-third session, ipog-io. P^dited by the Secretary. Pp. xxxii + 

 429 (Glasgow : The Ins.titution, 1910.) 



NO. 2195, VOL. 88] 



principle of this system was the driving into the ground 

 of a i6-inch diameter steel tube closed at the lower end 

 either by a loose point or a pair of hinged jaws, which 

 open when the tube is eventually withdrawn and permit 

 concrete, either plain or reinforced, to be passed through, 

 filling up the entire space originally occupied by the tube 

 simultaneously \yith the withdrawal of the latter from 

 the ground. This system has now been extensively 

 employed in the United States, and is rapidly coming into 

 use in this country ; the cost was stated to be about 

 25. 6d. per cubic foot of pile when no reinforcement was 

 used. 



The important problem of the design of surface con- 

 densers, more important than ever since the introduction 

 of the exhaust steam turbine, was dealt with in a paper 

 by Mr. R. M. Neilson, who stated that empirical methods 

 must be abandoned, and the area of cooling surface calcu- 

 lated in a rational manner so as to allow a given vacuum 

 to be guaranteed under given conditions. The author pro- 

 ceeded to work out a scheme for the design of condensers, 

 allowing for the varying conditions found in practice, and 

 then offered a series of valuable suggestions as to the 

 most profitable lines on which experimental research 

 might in the future be conducted. In the discussion Prof. 

 Mellanby directed attention to Dr. Stanton's researches 

 into this problem, and Mr. Weir pointed out that in a 

 condenser for a turbine-propelled torpedo-boat he was able 

 with a vacuum of 287 inches to secure a condensation of 

 27 lb. per square foot of cooling surface. 



Other papers published in this volume are steamship 

 repairs by electric and autogenous welding, by Mr. H. S. 

 Younger, descriptive of processes by which repairs can be 

 carried out either by electric welding or by means of the 

 oxy-acetylene process on damaged material so as to make 

 it serviceable again ; some tests on board ship to ascertain 

 the water consumption of engine-room and deck auxiliaries, 

 by Mr. C. F. A. Fyfe ; and Prof. Mellanby 's description of 

 a new experimental steam engine at the Glasgow and West 

 of Scotland Technical College. T. H. B. 



TICKS.' 



''PHE rapid advance that has been made in recent years 

 ■^ in scientific and medical knowledge with regard to 

 diseases caused by parasitic Protozoa and other micro- 

 scopic organisms has had the secondary result of directing 

 attention to the insects or other invertebrate animals which 

 are often the agents in the dissemination of the disease- 

 causing parasites. Mosquitoes, tsetses, and other biting 

 flies, fleas, and other ectoparasites are now being collected 

 eagerly and studied earnestly in all parts of the world, 

 less perhaps by professed zoologists than by medical men 

 and others, to whom the practical importance of these 

 pests is a greater stimulus to investigation than the purely 

 scientific interest which the creatures may possess in them- 

 selves. Hence special attention has been directed to the 

 various groups of blood-sucking arthropods so soon as 

 their connection with particular diseases has been made 

 known. Mosquitoes were the first to come into promin- 

 ence when their connection with malaria was discovered ; 

 then biting flies, and especially tsetse-flies, when their rdle 

 in disseminating trypanosomiases of animals and human 

 beings was made known ; and next fleas have been the 

 subject of close study, when their relation to the spread of 

 plague became apparent. There remain three important 

 groups of ectoparasites : ticks, lice, and bugs. It is well 

 known that ticks play a considerable part in spreading 

 diseases. In human beings, African relapsing fever is 

 caused by a spirochajte transmitted by a tick ; hence its 

 popular name of " tick-fever." In animals, various deadly 

 diseases, known collectively as " piroplasmoses, " because 

 caused by a minute blood-parasite belonging to the genus 

 Piroplasma, or allied genera, are known to be transmitted 

 by various species of ticks ; such are the " red-water " or 

 " Texas-fever " of cattle, and similar diseases of horses^ 



1 "Ticks, n Monograph of the Ixodoidea." ByG. H. F. Nuttall, O. 

 Warhurton, W. F. Cooper, and L. E. Robinson. Part i., BiblioRraphy of 

 the Ixodoidea, by G. H. F. Nuttall, L. R. Robinson, and VV. V. Coop'r. 

 Price 6s. net. Part ii., by G. H. F. Nuttall and C. Warburton. Price lajr. 

 net. (Cambridge University Press, tgti.) 



