-13- 



2a = 100cm, ^ = 198 cm 2h = I.14 cm, P = 32 atm. 



If we set up the quotient h/a and a//, a glance at Fig. 8 or at Table 1 

 shows that In the first case we must use for computation n = 5 and in the second 

 n = 4. Our formula (D) gives then, using E = 2 x 10"kg./cm^, p = 30 for the fir* 

 tube and p = 39 for *he second, which is about 23 per cent more than the observed 

 values. In order to give an estimate of this variation, It might be remarked thet 

 for the first tube the observed value p = 24 would result if the wall thickness 

 were about O.4 mm less and the effective ("massgebende" ) tube length about 10^ 

 greater. For the second tube, eq. (D) would give p = 32 atm. if instead of 11. 4 

 mm as v/all thickness, 10,8 mm be used. These are differences which may very pro- 

 bably be assumed in the whole range of the experiment since it was sought to at- 

 tain the most probable conditions in practice, not exact experimental conditions. 



Concerning the five experiments of Richards (Engineering, l88l,I p. 429. 

 Compare Wehage, Dlngler's Polyt. Jour. 1881, Vol.242, p. 236), two experiments, ac- 

 cording to the descriptions of the authors, were made on old, second-hand tubes 

 that were lapped and riveted and therefore must have shown marked departure from 

 the circular form. For a third experiment, the tube already had an observed 

 bulge. For these three oases, our formula gives approximately twice as high a 

 collapsing pressure as that actually observed. For the two other experiments 

 (welded and strap jointed tubes) the results were exactly as for the tubes of the 

 Danzig Navy Yard. 



The experimental values are: 

 2a = 96.5 cm, I = 218.5 cm, 2h = I.27 cm, p = 31.6 atm; 

 2a =137.1 cm, I = 91.4 cm, 2h = O.635 cm, p = 9.0 atm. 



The computation by formula (D) gives in the first case p = 45 atm. for 

 n = 3» and in the second p = 11. 9 atm. for n = 7* 111 order to obtain the observed 

 values from the formula, it is sufficient to increase the length about 10^, from 

 consideration of the defective support, and decrease the wall thickness about O.5 

 mm from consideration of the inequalities, the welds, etc. 



The experiments of Fairbairn (Trans. Royal Society, London, l858,p.389), 

 which were not undertaken with actual boiler flues, but with small, carefully pre- 

 pared models, furnish for the most part results which completely agree with our 

 computations. We choose three examples at random, or, to be exact, from those 

 which, according to Falrbairn's data, show the most uniform lobe formation. 



