116 REPORT — 1851. 



valve in its seat, and so keeps it constantly free and ready to rise whenever the pres- 

 sure attains the required force. 



Mr. Nasmyth exhibited several diagrams drawn by the valve itself, which gave 

 the most clear evidence of the existence and nature of the motion which the valve 

 derives from the action of the water on the sheet-iron appendage before named. 

 These diagrams were obtained by attaching a pencil to the top of the valve, and per- 

 mitting it to draw upon a card such figures as resulted from the slight but incessant 

 motion of the valve. The perfect action of this valve has led to its extensive 

 adoption. 



On a Direct Actio?i Steam-Fan for the more perfect Ventilatio7i of Coal Mines. 

 By James Nasmyth, C.E., F.R.A.S.. 



Mr. Nasmyth exhibited drawings and gave a description of his direct action steam- 

 fan which he' had contrived and arranged for the purpose of improving the ventila- 

 tion of coal mines. The fan is one of the most efficient and simple agents for moving 

 great masses of air, and operating through the agency of centrifugal action ; the 

 quantity of air which it can draw in at its central opening is exactly equal to what 

 it can blow out or distribute from its circumference ; and although we are most fami- 

 liar with the action of fans as blowing agents, yet the suction powers of fans are 

 equally effective, and it is this suction power which Mr. Nasmyth proposes to em- 

 ploy as the means for the better ventilation of coal mines. In this respect the appli- 

 cation of fans for the jiurpose in question is not novel ; but the efficiency of these 

 powerful and otherwise simple machines has been much impeded by the complex 

 and troublesome apparatus which has hitherto been employed for transmitting the 

 required high rotative velocity to them, such as by the use of straps, belts and 

 pulleys, and other agents employed in converting the slow motion of a long-stroked 

 engine into the high velocity of rotation required by such fans. 



The chief feature of novelty in the fan proposed by Mr. Nasmyth, consists in the 

 application of a short-stroke steam-engine working direct on to the spindle or axis 

 of the fan, on the end of which the crank of the engine is placed ; by this system of 

 arrangement all intermediate gearing and machinery is done away with, and the 

 power of the steam made to act in the most direct manner on the fan. The dia- 

 meter of the fan described by Mr. Nasmyth is 6 feet, the stroke of the engine 4 inches ; 

 the diameter of the cylinder of the engine being 12 inches, this, worked with steam 

 of a pressure of 30 lbs. to the square inch, produces a rate of motion on the fan of 

 650 revolutions per minute ; and as the fan blades are 2 feet wide, the rate of dis- 

 charge in cubic feet per minute is equal to 23,000 ; and as the ingress apertures at 

 each side of the fan are in direct communication with the up-cast shaft of the mine, 

 a corresponding quantity of air will descend the down-cast shaft and pervade the 

 workings. An important advantage of this mode of ventilation will be, that the ven- 

 tilating agent, namely, the fan, is at all times visible, open to inspection, being placed 

 on the surface of the ground, and in that respect free from danger ; and even in the 

 event of any explosion in the pit, the means of reventilating is by its means at hand. 



On an improved Apparatus for Casti7ig the Specula of Reflecting Telescopes. 

 By James Nasmyth, C.E., F.R.A.S. 



On a Method of condensing Steam in Marine Engines, at present eftnployed 

 in several Steam Vessels in the Bristol Channel. By Joseph T. Price 

 of Neath Abbey. 



It is well known that Boulton and Watt, when they took out their patent for 

 their steam-engine, tried the effect of surface condensers, and proved the superiority 

 of condensing by a jet of water in land engines ; but it is also well known that at 

 that period marine engines for giving motion to ships on rivers and the sea had not 

 been used. Had marine engines been in use at that time, it may fairly be supposed 

 that Boulton and Watt would not have omitted to show the adaptation of the cold 

 water through which a vessel passes to the purpose of condensation and feeding the 

 boiler with hot water freed from salt, &c. 



