Handbook of Railroad Construction; For the use of American engineers. / Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States.

by George L. Vose

Diameter two inches, surface 1466, length fourteen feet, we have,

N = 1466
14 × 0.167 × 3.1416 = 200.

375. Table 10. Giving the number and dimensions of tubes to obtain any given amount of surface.

L’gth.	Diam. 1½	Diam. 1¾	Diam. 1⅞	Diam. 2	Diam. 2⅛	Diam. 2¼	Diam. 2⅜	Diam. 2½	L’gth.
8	314	336	397	419	445	471	504	523	8
8½	334	389	422	445	473	500	535	556	8½
9	352	411	447	471	507	530	566	588	9
9½	372	435	471	497	523	559	597	621	9½
10	392	457	496	524	556	589	628	655	10
10½	411	480	521	549	584	618	659	687	10½
11	431	503	545	576	612	647	690	720	11
11½	451	526	570	602	640	677	721	753	11½
12	471	549	595	628	667	705	752	786	12
12½	490	572	620	654	695	735	783	818	12½
13	510	595	645	681	723	764	814	851	13
13½	530	617	669	707	750	793	845	884	13½
14	549	640	695	733	778	823	876	916	14
14½	569	663	719	759	806	852	907	949	14½
15	589	686	744	785	834	882	938	982	15
15½	608	708	769	811	861	911	969	1015	15½
16	628	731	794	837	889	941	1000	1048	16
16½	648	754	819	863	917	971	1031	1081	16½
17	668	777	843	889	945	1000	1062	1114	17

FORMULA.

13.5√a – 28,

where a is the percentage of admission.

Example.

What is the mean pressure, with an initial pressure of one hundred pounds, and sixty per cent. admission.

13.5√60 – 28 = (13.5 × 7.7) – 28 = 76
100 of 100, or 76 lbs.