June 15, 1876] 



NA rURE 



'59 



49 inches at Scopello, and 69 inches at Oropa. The two abso- 

 lutely largest daily falls occurred on the 5th, viz., 89 inches at 

 Crabbia, and 9-1 inches at Mesma. Tart iv. of the paper deals j 

 with the general causes determining the lainfall of Italy and the 

 application of the results in explanation 'of the mode of the 

 peculiar distribution of the rainfall over Italy during 1872. 



Macmillan and Co. will shortly publish the second part of 

 Mr. Pickering's " Physical Manipulation." 



The annual meeting of the Aeronautical Society was held on 

 the 7th inst., Mr. Charles Brook, F.R.S., presided. A paper 

 was read by Mr. D. S. Brown on the advantage of applying 

 power for aerial propulsion in an intermittent manner, and on 

 the soaring of birds. Another paper by Mr. Armour, C.E., on 

 air compression under wing-planes, was read. 



The fiftieth anniversary of the Socle'te Industrielle de Mul- 

 house has been celebrated by an Exhibition of ihe Arts and 

 Manufactures of Alsace. M. Perrot, one of the original founders, 

 read the report, which showed that the Society has had a pros- 

 perous and useful career. Papers were read on the electric light, 

 illustrated by the illumination of the banquet hall by electricity ; 

 on steam-engines ; on borings at a great depth executed in 

 Alsace ; on electro-chemical experiments made on benzol. The 

 meeting was a most successful one. 



The following additions have been made to the Royal West- 

 minster Aquarium during the past week : — Young Green Turtle 

 {Chelonia viridis) from the Island of Ascension, presented by 

 officers of the Challenger expedition ; Monk-fish (Rhina squatina) ; 

 Blue and Red Wrass {Labrus tnixius) ; Greater Weever [Tta- 

 chinus draco) ; Horse Mackerel {Trachurus trachnrus) ; Angler- 

 fish {Lophius piscatorius) ; Gattoruginous Blenny {Blennitis 

 gatloruqini) ; Red Gurnard ( Trigla lyra) ; Grey Gurnard 

 (T. gurnardus); Streaked Gurnard [T. lineaia) ; Lump-fish 

 (Cyclopterus luinpus) ; Sea Lamprey Pdromyzcn marinus) ; Mud 

 Lamprey {Ammoccetes branchialis). 



The additions to the Zoological Society's Gardens during the 

 past week include among others, a Mexican Deer {Cervus mexi- 

 canus) from S. America, presented by Mr. Thos. B. Forwood ; 

 two Spur-winged Geese {Plectropierus gambensis) from S. Africa, 

 four Galapagan Tortoises ( Tediido elephanio/us) from the Gala- 

 pagos Islands, deposited ; a Humboldt's Lagothrix {Lagothrix 

 hiimboldti), an Ocelot {Fdis pardaiis), a Tayra [Galiciis barbara) 

 from S. America; a Great Barbet {Megahvma vhens), from the 

 Himalayas, purchased. 



LOAN COLLECTION OF SCIENTIFIC 

 APPARA TUS 



SECTION— MECHANICS 

 PRIME MOVERS^ 

 U AVING thus mentioned the earliest record of hydraulic (or 

 -*^ indeed of any) prime movers I will not endeavour to trace 

 iheir history down to modern times, as it would be impossible to 

 do so usefully within the limits of an address. I will therefore 

 now ask you to join me in considering what are the conditions 

 which govern the application of water to hydraulic prime movers. 

 After all water must be looked upon as a convenient form of 

 descending weight. When the fall is not great it is always prac- 

 ticable by means of water-wheels having buckets which retain 

 the water to employ, as I have said, its mere gravity, and pro- 

 bably it is by this mode that the highest result is procured from 

 any given quantity of water falling through a given height. By 

 the use of a backshot wheel as much as 75 per cenf. of the total 

 power is obtainable. The 25 per cent, ot loss arises from the 

 friction of the axle of the wheel and of the gearing transmitting 

 the force to the machine which is to utilise it, from some of the 



I Address delivered by V. I. Bramwell, C.E., F.R.S., one of the vice- 

 presidents of the Section, May 25. Continued from p. 141. 



water being discharged out of the buckets before the bottom of 

 the fall is reached, from the necessary clearance between the 

 wheel and the tail water, from the eddies produced in the water 

 as it enters the buckets, and (to a certain small extent) from the 

 resistance of the air. 



When the difference of level between the source of water and 

 its delivery exceeds, however, 40 or 50 feet, the water-wheel 

 becomes so unwieldy and expensive and revolves so slowly that 

 it ceases to be a desirable prime mover ; recourse can then be 

 had to water-pressure engines, engines wherein pistons move in 

 cylinders and being pressed alternately in opposite directions by 

 the head of water set up rotary motion in the machine in the 

 same way as if the pistons were acted upon by steam. In the 

 construction of such water-engines great care must be taken to 

 have ample inlets and outlets in order that the loss . incurred 

 either by the power requisite to drive the water through restricted 

 orifices, or by surface resistance caused by a too speedy flow along 

 the various passages may be a minimum. Care has to be taken 

 also in the arrangements of the valves that the engines, when 

 employed for rotatory movement, may be able to turn their cen- 

 tres without producing an injurious pressure upon the water 

 within the cylinders. Water-engines employed for pumping, but 

 without rotatory movement, are mentioned by Belidor in his 

 "Architecture Plydraulique," published in 1739, article i, 156. In 

 England Sir William Armstrong has brought these machines to 

 great perfection. The first of these, erected many years ago, is 

 still working most successfully at the Allan Head Lead Mines. 

 This machine is driven by a natural head of water and not from 

 an accumulator, and is employed in the mine as a winding 

 engine. 



An extremely useful feature in engines of this kind is their 

 adaptability to be driven by the pressure of water derived from 

 an ordinary water-work?, and in this manner small manufac- 

 turers carrying on business in their own houses are enabled to 

 obtain a prime mover with great ease, and, all things considered, 

 at small cost. Not only is advantage taken of such machines 

 for the purpose of driving m aiufactories, but water cylinders are 

 now largely employed for working the bellows of church organs, 

 for which purpose an overshot water-wheel is shown as being 

 employed as far back as Solomon de Caus's book, date 1615. 



Large water-wheels, or even water-engines, are comparatively 

 costly machines, and as large water-wheels make but few revolutions 

 per minute, they require, as has been said, expensive and heavy 

 gearing to get up speed ; thus it is that it frequently becomes a 

 desirable thing to dispense with such machines and to resort to 

 other modes of making available high falls of water. In former 

 times this was done by suffering the impetuous stream of water 

 to beat upon the pallets of v.ater-wheels, but from such machines 

 only a poor effect could be obtained, as a large portion of the 

 energy m the water was devoted to the formation of eddies and 

 the generation of heat, and to the production of lateral currents, 

 leaving but a small percentage available as motive power. 



Much of the evil effect, however, attendant upon using the im- 

 pact of water as a means of driving water-wheels is obviated by 

 the construction invented by the distinguished French engineer 

 Poncelet. For high falls, however, the implement now gene- 

 rally employed is the turbine, of which the well-known Barker's 

 mill may be looked upon as the germ. 



I have got before me No. 1,983, a model of Fourneyron's 

 turbine. 



This is not an apt model for my present purposes, inasmuch as 

 it is one to be employed with a comparatively low fall of water, 

 but even in such instances the turbine gives most excellent results, 

 and it has the advantage over the water-wheel of being able to 

 work with great efficiency although there may be a considerable 

 rise in the " tail water," a rise which would materially check the 

 action of an ordinary water-wheel. In this turbine every care 

 has been bestowed to give a proper form to the pallets on which 

 the water acts so as to take up step by step as it were the whole 

 of the energy residing in the sircam, so that the water may pass 

 away from the turbine in an inert condidou, and s- that in acting 

 upon the vanes of the turbine, eddies may not be formed and thus 

 energy may not be wasted. 



There are probably few sights more surprising to the old- 

 fashioned mechanic, who has been used to see water-wheels of 

 50 or even 70 feet diameter employed for the utilisation of a high 

 fall, than that of a turbine occupying only a few cubic feet of 

 space but running at such a velocity as to consume the whole of 

 the water of a considerable stream, and so to consume it as to 

 deliver nearly as large a percentage of useful etTect as would the 

 cumbrous water-wheel iticl'. 



