180 



Transactions of the Horticultural SociefT/. 



directly, and the equivalent head is inversely as the area of the section of 

 the pipe; consequently, 



J- — = — ^l!L. = the head equivalent to the friction. 



•7854 di d ^ 



But, in a pipe near the top, the head producing the velocity and overcom- 

 ing the friction is the quantity the fluid rises by expansion, ov he ; there- 

 fore. 



A.{h ; J^ — \= v~' 'y whence \/ . 



Khe d 



d + ixlf 



The effect of the cohesion of the fluid does not produce a sensible effect in 

 practical cases j but, if it had been considered, the result would have 

 shown that the pipe might be so small in proportion to its length as to 

 render the velocity nothing. 



" 8. The coefficients to be obtained from experiment are denoted by 

 A, e, and/. That denoted by a depends only on the form of the tube or 

 pipe at its junction to the boiler, being the same for all fluids. 



" For the common mode of joining (fig. 22.) it is a=42; but, for a 

 pipe with a conical entrance (fig- 23,), it is a =62. Now, the expense of 



the conical fonn renders it probable that it will seldom be used ; hence, 

 42 may be inserted in any rule for general purposes. 



" 9. The expansion of liquids not being perfectly equable by equal in- 

 crements of temperature, and not the same for all liquids, the easiest mode 

 for obtaining it for any particular case will be by means of a table. 



Table of Exjninsion of Liquids. 

 Expansion by 1° of heat at the temperature in the first column. 



If the difference of temperature, for example, be 8°, and the mean temper- 

 ature 172°, then, for water, 8 X '00035 = -0028 is the expansion of water by 

 8° of heat, and 8 X •00038=^00304 is the expansion for a saturated solution 

 of salt. 



" 10. The friction of fluids, and particularly the effect of change of tem- 

 perature, has been investigated only in a very partial manner, [Here Mr. 



