August 6, 1891] 



NATURE 



IIZ 



one of difficulty ; and it may be said that it has not yet been solved. 

 The most serious effort yet made was the building of a granary 

 on the banks of the Thames, known, we believe, as the Patent 

 Ventilating Granary. This granary was referred to during the 

 discussion by Mr. Percy Westmacott, so long the chief of the 

 hydraulic department at Armstrong's. The patent ventilating 

 arrangement consisted of a perforated tube running down the 

 centre of each bin. This was provided with a movable stop or 

 plug, and, by adjusting the height of the stop, ablast of air could 

 be directed through the perforations of the tube into any part of 

 the grain. The idea was of French origin, and, Mr. West- 

 macott said, more ingenious than practical, so that the granary 

 was pulled down after a time. It is easy to understand that 

 those parts of the grain which required most ventilation would 

 form into hard lumps, into which the air would not penetrate. 

 As a matter of fact it is found more advantageous to air the 

 grain by giving it a constitutional over the carrying bands. 



Prof. Hele Shaw's paper on his experimental engine and 

 alternative centre-testing machine was one of great interest. 

 The engine in question, which is described as a marine engine, 

 though it has a large fly-wheel, is, we believe, the most 

 elaborate from an experimental point of view, yet made. 

 The question has been raised whether it is not too elaborate, 

 so that satisfactory results will not be reached on any one 

 point. That is a problem which remains to be proved by 

 facts ; for the engine has only just been erected. It is 150 horse- 

 power, and is of the ordinary vertical three-cylinder three-stage 

 compound type. The high-pressure and intermediate cylinders 

 have cylindrical valves, and the low pressure has a flat 

 valve. Each valve is worked by a different type of 

 motion — namely, ordinary Stephenson link motion, Joy gear, 

 and Hackworth gear. The cylinders are jacketed at sides 

 and ends, and there are provisions in the way of con- 

 nections for working in every possible manner, i.e. 

 cylinders all jacketed, not jacketed at all, or any one or two 

 jacketed. Any comljination of cylinders can be worked, or 

 any one cylinder alone. In addition to this the cranks are 

 adjustable on their shaft, so that any combination can be got in 

 this way ; in short, the number of different combinations that 

 are at command would require years to work through. There 

 are the usual measuring tanks and other apparatus for quantita- 

 tive tests. An excellent suggestion was made by Prof. Good- 

 man during the discussion. He proposed that arrangements 

 should be made for testing the students' knowledge by putting 

 the engine into conditions not in accordance with proper design. 

 For instance, he would have valve-rods or excentric rods of 

 improper length, valves ill-set with improper lap or lead, leaky 

 valves and pistons, and various other ills, to which engines are 

 subject, purposely introduced. He would also provide a means 

 of passing water into the cylinders. He would then have the 

 student take diagrams from the engine, and leave him to deter- 

 mine the cause of the defect by the appearance of the cards. 

 We hope Prof. Goodman will be able to follow up this useful 

 suggestion in his own laboratory at Leeds. The alternative 

 testing machine is a 1 00- ton single-lever machine of the 

 Wicksteed type. The alteration in power is got by substi- 

 tuting one fulcrum for another a few inches distant. The 

 mechanism by which this is done is ingenious, but the details 

 would be difficult to explain without the aid of diagrams. 



The last paper read at the meeting was that of Mr. Leader 

 Williams. The author commenced by saying that 46^ million 

 cubic yards had to be excavated in making the Manchester Ship 

 Canal, and as only 17,000 men and 200 horses have been used 

 there was evidently required a large power in the shape of 

 mechanical appliances in order to get the work done in anything 

 like reasonable time. Ninety-seven steam excavators and eight 

 steam dredgers of large power have been employed ; and the spoil 

 has in most cases been taken a distance of several miles. For this 

 work, and for the general purposes of construction, 173 locomo- 

 tives and 6300 trucks and waggons have been used. The railways 

 laid for the purpose amount to 228 miles of single line. The rate of 

 excavation has varied from three-quarters of a million to \\ 

 million cubic yards per month. There are also employed on the 

 works 124 steam-cranes, 192 portable and other steam-engines, 

 and 212 steam-pumps. Ttie coal consumed by the engines is 

 about 10,000 tons a month. These figures will give some idea 

 of the heroic proportions upon which large constructive works 

 are carried out, and the capital required to start them. The 

 whole plant of the Manchester Ship Canal has cost, we believe, 

 close on a million sterling. The machines described in the 



paper which were of greatest interest were the excavators. 

 The chief of these is the now well-known "steam navvy," 

 made by Ruston and Proctor, of Lincoln. It first came pro- 

 minently into notice during the construction of the Albert 

 Docks, and is looked on as a standard tool wherever large 

 excavating work is undertaken. It has the immense ad- 

 vantage of being able to work in any kind of soil, even 

 including sandstone rock, if not very hard. It is only in 

 hard rock that blasting has to be done as an auxiliary. 

 The most interesting, or, perhaps, we should say the 

 most novel machines are the French and German excavators, 

 or land dredgers, which have been introduced into this country 

 for the first time in connection with this work. These are on 

 the same general principle as a floating ladder and bucket 

 dredger of the common type. In place of the ladder and 

 motive machinery being held by a floating hull, there is a small 

 house mounted on wheels, and this runs on a line of rails on the 

 summit of a bank. The ladder slopes outward from the side, 

 reclining on the bank, which the buckets scrape away as they 

 traverse, and deposit the spoil in waggons on the bank above. 

 There are differences in detail between the French and German 

 types, but in general principle they are alike. The German 

 machine appears to us the better designed, but Mr. Leader 

 Williams says the French excavator is of more substantial 

 construction. The weight of these machines is from 70 to 

 80 tons, and under favourable conditions they have' been 

 known to excavate the enormous bulk of 2400 cubic yards in one 

 working day. Mr. Williams's paper was not discussed, which 

 is a fact to be regretted by engineers, as the subject is one which 

 requires ventilation ; but time was running short. After the 

 usual votes of thanks, the sittings of the meeting were brought 

 to a close. 



We can only add a few words about the excursions. On the 

 Tuesday there was a lunch on board the big White Star liner 

 the Majestic, for one section of the members ; whilst others 

 visited the grain warehouse, described by Mr. Shapton in his 

 paper, and the new overhead railway, which has been designed 

 by Mr. Greathead, the Engineer of the City and South London 

 Railway, and which runs along the line of docks. This railway 

 is of steel and iron throughout, and possesses the novel ad- 

 vantage of forming a water-tight roof, under which the people 

 of Liverpool will be able to walk on rainy days without getting 

 wet. In the evening there was a conversazione, which, of course, 

 was the social feature of the meeting. On Wednesday afternoon 

 the members visited the new engineering laboratories which have 

 been added to University College, Liverpool, where the engine 

 and testing machine described in Prof. Hele- Shaw's paper were 

 examined. On Thursday one party visited the Mersey Docks, 

 the Mersey Tunnel, and Laird Bros.' ship-yard and engine works. 

 At the latter there are several interesting vessels in progress, in- 

 cluding the big battle ship Royal Oak, of 14,000 tons. Another 

 party went to Horwich, and saw the fine locomotive works which 

 have just been completed there by the Lancashire and Yorkshire 

 Railway. These works have been beautifully planned and laid 

 out under the superintendence of Mr. Aspinall. Although not so 

 large as some other establishments of a similar kind, they may 

 be taken as a model of design. Mr. Aspinall naturally had a 

 unique opportunity with a clear field to work upon, and an 

 accumulated experience at his command. Friday, the last day, 

 was devoted wholly to the Manchester Ship Canal, the members 

 being carried down the line of works in a special train, under 

 the guidance of Mr. Leader Williams. 



NO. IT 36, VOL. 44] 



THE NEW GAS, CHLOROFLUORIDE OF 

 PHOSPHORUS. 



AS briefly announced in the report of the proceedings of the 

 French Academy of Sciences, a note upon a new gaseous 

 compound, containing phosphorus, fluorine, and chlorine, has 

 just been presented by M. Moissan, on behalf of M. Poulenc. 

 During the course of his work upon the fluorides of phosphorus, 

 M. Moissan observed that, when phosphorus trifluoride was 

 brought in contact with chlorine, the green colour of the latter 

 at once disappeared, and there appeared to be formed a new 

 and colourless gas. The gas thus formed has been prepared in 

 considerable quantity by M. Poulenc, and its properties inves- 

 tigated. It appears to be directly formed by addition, according 

 to the simple equation — 



PF3 -H CI2 = PF3CIJ ; 



