534 Royal Society ;— 



corresponding to 2 molecules of ammonia, like many other poly- 

 ammonias, is raonoacid. 



The analysis of the hydrochlorate leads in fact to the formula 



Co6Hi2N2,HCl. 

 The platinum-salt contains 



C26Hi.,N2,HCl,PtCU. 

 The new derivative of aniline undergoes several remarkable changes 

 which require further elucidation. 



" Note sur un Organe, place dans le Cordon Spermatique, et dont 

 I'existence n'a pas etc signalee par les Anatomistes." Par F. Giraldes, 

 Professeur Agrege de la Faculte de Mcdecine, &c. 



" On Chonclrosteus, an Extinct Genus of Fish allied to the Stu- 

 rionidse." By Sir Philip de Malpas Grey Egerton, Bart,, F.R.S. 



May 20. — The Lord Wrottesley, President, in the Chair. 



The following communications were read : — 



" On the Resistance of Tubes to Collapse." By William Fair- 

 bairn, Esq., C.E., F.R.S. &c. 



The object kept in view bj'- the author of these researches was to 

 determine the law which governed the resistance of cylindrical tubes 

 to external uniform pressure. The anomalous condition in which 

 these constructions have been placed in reference to the internal flues 

 of boilers, and the frequent fatal accidents from explosions produced 

 by collapse, have imperatively called for inquiry into the causes which 

 have led to these unfortunate results. Ever since the first introduc- 

 tion of the steam-engine as improved by Watt, and especially since 

 the increased demand for its construction, and its application to 

 almost every branch of industry and every system of transit, the 

 consideration of all circumstances which may affect its economy and 

 security, has become of vast public importance. 



During the more early period which followed its first introduction, 

 the form of boiler and its powers of resistance to strain, were con- 

 siderations of much less importance than at present. Then the force 

 of steam, or the pressure under which it was generated, was only 

 about one-eighth, and in some cases less than a sixteenth of what it 

 now is. Besides, the fertde genius of Watt had provided against 

 accident, by a self-acting apparatus, which regulated not only the 

 pressure, but the supply of water to the boiler. Since that time a 

 total change has taken place in the construction and working of the 

 steam-engine ; and boilers which were perfectly safe at 7 lbs. upon the 

 square inch, are absolutelj'^ inadequate for generating steam at 40 lbs. 

 to .50 lbs. on the square inch. This being the case, it follows that every 

 precaution becomes urgently necessary which may serve to increase 

 the strength, and equalize the resisting power of vessels containing 

 an element of such potent influence, and yet so essential to the com- 

 forts and enjoyments of civilized life. 



Entertaining these views, the author goes on to say, that hitherto 

 it has been considered an axiom in boiler engineering, that a cylin- 



1 



