HYDRODYNAMICS. 



537 



In order to shew the method of using this Table, 

 ! t u< take the cue of the * J inch pipe which convey* 

 water to Edinburgh. In this case, (see p. 5-iO, Exam- 

 ple 1 1.) we have 



Reduced to Metres. 



H= 51 feet 15.54 



D = 0.575 0.1143 



/ = 1*930 4550.4 



' = 553 = - 34151 



Since the value of D = 0.1143 is in tenth parts of a 

 metre, we must enter the lower part of Table VI. in 

 column 1, and by taking proportional parts, it will be 

 found that the value of Q corresponding to D, and to 

 the value of i = 0.0034151 is 0.005104 parts of a cu- 

 bic metre, which being multiplied by 61023.5, the num. 

 ber of English cubic inches in a cubic metre, gives 

 311.46 cubic inches discharged in a second. By mul- 

 tiplying this by 6O", and dividing the product by 

 103.4, the number of cubic inches in a Scotch pint, we 

 obtain 180.7, as the number of Scotch pints that the 

 preceding pipe ought to discharge in a minute, accord- 

 ing to Prony's Table. 



The following comparison of the results of the diffe- 

 rent formulae will be interesting to the reader. 



Scotch Pints. 



Quantity of water actually discharged by the pipe 1 89.4 

 Do. by Eytelwein's formula .... 189-77 



Do. by Girard's formula 188.26 



Do. by Du r.uat's formula 188.13 



Do. by Prony's simple formula . . . 192.S2 

 Do. by Prony's Table 180.7 



This comparison is by no means favourable to Prony's 

 formulae. 



SICT. IV. Account of the Experiment! of Dv Bual and 

 Girtird, on the fffect of Heat upon the Motion of Wa- 

 ter in Marrow Pipe*. 



THE effect of heat in augmenting the fluidity of wa- 

 ter, seems to have been noticed at a very early period. 

 Plutarch informs us, that the clepsydrae, or water 

 clocks, went faster in summer than in winter, which 

 he seems to ascribe to an increase of fluidity. Exv- 



tvra y{ i \J-vxnK T wi*{ wt4H fttt^o x 

 trrir n TI< >..vi/3ji ( tumftutuw, /3jaJ> 

 fun* i *{*< Quett. Natural. 



M. Du Buat made a series of experiments on the ef- 

 fect of heat upon the velocity of different fluids dis- 

 charged from small tubes ; but these effects were not 

 very striking, as he employed tubes of too great a diame- 

 ter. The results which he obtained are shewn in the 

 following Table. 



Motion ct 



Water in 



Pipes and 



Canals. 



Tlieeflect 

 of licit in 

 promoting 

 fluidity 

 known to 

 the an- 

 a emu. 



Du BuaTt 

 experi- 

 ments. 



TABLE Containing Du Buat'i Experiment on tne Motion of different Fl*idt, at different dt greet of temperature 



in Tubet of Clan. 





From these results Du Buat concludes, that water 

 mores less rapidly as it approaches to congelation, 

 and that it runs more rapidly as its temperature in- 

 that salt water runs more slowly than rain 



water at the same temperature ; that spirit of wine 

 runs perceptibly less rapidly than water, on account of 

 its viscosity, or its great adhesion to the sides of the 

 tube ; and that mercury which, when it is very pure, 



VOL. XI. FART II. 



fast an reduced to metres by dividing them by 3.MI- 



3 v 



