By Mr. Thomas Tredgold. 



575 



common water, in its effective state for affording heat, we 

 may take '0014 for the value of/; and, '0015 for salt water, 

 not very different from sea water. 



11. By inserting those values for/ in the formulae, and 42 

 for A, we have for common water, 



* S d + h *hj i = d + -335f = v > an(i ** or sea water v^^jrp = v- 

 In these k is the depth of the boiler below the centre of the 

 upper pipe in feet ; / the length of pipe the liquid has to 

 move through in its course from the boiler and back again ; 

 d the diameter of the pipe in inches ; e the expansion of an 

 unit in mass of the fluid by the difference of the mean tem- 

 peratures of the boiler and reservoir ; and v the velocity in 

 feet per second ; whence the quantity of fluid cooled, and, 

 consequently, the quantity of heat afforded by the apparatus 

 is known. 



12. From the common principles of hydrostatics and the 

 equations we have obtained, the following practical deduc- 

 tions may be derived. 



1st. The more expansible the liquid is by a given change 

 of temperature the greater will be the velocity. 



2d. All other things being the same, the velocity will be 

 increased in proportion to the square root of the depth 

 of the boiler ; therefore, in a boiler four times as deep, the 

 velocity will be doubled. 



3d. If there be sufficient service of pipe for the object re- 

 quired, a reservoir is not necessary to the motion of the 

 water ; a simple bent pipe (fig. 4) being all that is essential 

 to motion ; the reservoir is only to reserve a hot mass of 

 water to maintain the heat after the fire has gone out. 



