420 
REPORT—1854. 
resulting from its pressure capable of the most perfect control, by means of 
the valves which regulate the inlet and outlet passages of the machines; but 
this very property, which gives so much certainty of action, tends to cause 
shocks and strains to the machinery, by resisting the momentum acquired 
by the moving parts. Tuko, for example, the case of an hydraulic crane 
swinging round with a load suspended on the jib, the motion being produced 
by the water entering on one side of a piston and escaping from tie other. 
Under such circumstances, if the water passages be suddenly closed by the 
regulating valve, it is obvious that the piston, impelled forward by the mo¬ 
mentum of the loaded jib, but met by an unyielding body of water deprived 
of outlet, would he brought to rest so abruptly, as to cause, in all probability! 
the breakage ot the machine. So, ;,!-■> in imwing a heavy weight "'iin 
considerable velocity, if the escape-passage he too suddenly closed, a simikir 
risk of injury would arise from the abrupt stoppage of the weight, it a 
remedy were not provided ; but these liabilities are effectually removed br 
applying, in connexion with the water passages to the cylinder, u sma 
clack-valve, opening upwards against the pressure into the supply P'l*» 50u 
to permit the pent-up water in Lite cylinder to .be pressed back into the pip 1 -' 
whenever it becomes exposed to a compressive force exceeding the pressure 
on the accumulator. By this means all jerks and concussions arc; avoidJ 
and a perfect control over the movement of the machine is combined wuu 
great softness of action. I(! , 
With regard to the kind of valves used for water-pressure machines, B"' 
that ether ift-valvea or slide-valves may be effectually applied, and k P 
b ht under heavy pressures, provided that sand be excluded from the 
and the valves be made of proper material. , ,, )|vin , 
shcavS? S u M ' l,0re a more Prolonged movement is required than m ¥ J* 
struetfon r 0m ; ome,lt, y a®**!, • employ rotative machines of various 
inenf n S ’• ! ur beav y pressures, such as an accumulator affords, ai • 1 
Teenn T ng , ?' lingers. emiuceted with a triple crank, and > ' 
Pl ! nn ‘ a r »f. 0,nbl ; inoe t( > a three-throw plunger pump, is welUdap* L^\ 
down to /•'? admission and exhaust valves are mUred spindtaPj f(ir 
tliat nnv WGlg lts and * eVL ' rs » and lifted in proper rotation by can s • ^ 
renef P eh?L 0Se i Up 7 l a •haft, and these valves rtf fife* 
take nl*i 8 , 0 ,v ‘ ate the concussion which would otherwise 
The li e K a m thc ‘ ura of eHch *"*«?. a he frost W 
often beenn U "* ' rater 'l ,l '» 'Siire machinery to be derange J . aV0 b- 
serve fir t* n U 5t ( 83 an objection to its use; and upon this po UM . 
whence 1 W experienced any interference from ^ c ,- 
the crmmd 7?*° 113 «**y * 
avoidably ’ ° r j ltm * ;i l,u <Iding ; and secondly, that wbL ' a[er in 
frostv wl^h F0Se , f1, aI1 ,isk bJ prevented by letting out the 
W hen M 101 wbpnevtT the machines erase working. the pa* 
sure r-n .ll m ° V , m S P° wer consists of a natural column of ' vatP ’ lpVC d f' r 
ro[ativei eXCetMl8 . 250 ° r *»* 1 KTS** 
in some dear" R |? air c f Under* and pistons, with slide-valv < ^ p 
prevent shock at° ^''^-pressnre engine, but bav,D £ [ a slide-** 
adapted for * turn ° r *trt,kc. Plate 11 1. fig* VKE& of +* 
are equally armljcahrf a N’ arrttU8 " f » onuic, hut the vcbef-c^ j(lqU ev 
tion. 1 T r &£* «^r-prcs>ure engine of 
as to aftml c,acks °pen against t ie pressure in tue ; t „ p m' 
cyl rnlcr when Z* V \ for the "***. which would otherwise beJ, ,» 
ui s,i'g : P “ r st c, °. cs ' a,,d Uiu t er ns 01 “ p 
b p pe, so as to draw m a portion of waste water 
