394 



Mr. A. H. Gibson on the Resistance to 



(2) Experiments by M. Stockalper on the pipe-line for 

 supplying compressed air to the working face of the St. 

 Gothard tunnel. These results are taken from the Proc. 

 Inst. C. E. vol. lxiii. p. 348. The pipe-line consisted of two< 

 parts, the first being partly of cast and partly of wrought 

 iron, while the second was of wrought iron, the whole having 

 flanged joints and rubber joint-rings. The first portion of 

 the pipe was 15092 ft. long and 7 '87 inches (-656 ft.) in 

 diameter, the mean velocity ranging from 15*6 to 19*3 ft. 

 per sec. The second portion was 1713 ft. long and 5*9 inches 

 (*492 ft.) in diameter, the mean velocity ranging from 29 

 to 37 ft. per sec. The mean pressure in the pipes ranged 

 from 53 to 80 lbs. abs. per sq. ins., while the mean tem- 

 peratures were 70° F. in the large and 79° F. in the small 

 pipe. 



Table II. 



Expt. 



i 



la 



lb 



2a 



3a 



3b 



Pipe. 



lbs. per sq. inch. 



I'm . 

 ft. per sec. 



Length 



_! fc _ 



15092 1 

 1713 J 

 15092 

 15092 i 

 1713) 



Diam. 

 ft. 



•656 

 •492 

 •656 

 •656 

 •492 



Pi- 



lh- 



pm. 



dp. 



82-3 

 770 

 64-0 

 564 

 53-6 



770 



736 

 60-8 

 536 



520 



79-6 

 75*5 

 62-4 

 550 



52-8 



5-29 

 3-52 

 3-24 

 2-79 

 1-56 



19-32 

 3714 

 16-30 

 15-58 

 29-34 



(3) Experiments by Dr. Brix (Proc. Inst. C. E. vol. xliiL 

 p. 184) on wrought-iron pipes 103 ft. long, and having 

 diameters of 3'25, 5*2, and 6'75 ins. ('271, -433, and -5625 ft). 

 The mean pressure was approximately atmospheric throughout, 

 the mean velocity ranging from 23'3 to 42 ft. per sec. In 

 these experiments the temperature is unknown, but is probably- 

 about 65° F. 



Owing to the comparatively small length of the pipes, the 

 head equivalent of the kinetic energy at exit and of the loss 

 at entrance forms a large proportion of the total pressure 

 drop. The sum of these losses has been taken as approxi- 



v 2 

 mately 1*5-^- , and allowance has been made for this in 



"j 

 calculating Sp. 



