88 REPORT 1842. 



It results from this table, that the Devonian system contains not less than fifty- 

 five species of fossil fish belonging to twenty different genera ; a number more than 

 ten times that which was nominally known in the entire series of formations of the 

 British Islands ten years ago. Who at that time would have believed that fifty-five 

 species of vertebrated animals would have been discovered in one of the formations 

 of the transition rocks ? 



Appendix to a Report on the Strength and other Properties of Cast 

 Iron obtained from the Hot and Cold Blast. By William Fair- 

 bairn, Esq. 



The experiments, of which the present is a notice, were entered upon in 

 March 1837, and subsequently the British Association did me the honour to 

 print them in their seventh volume of Transactions. They were intended to 

 determine an important quality in the strength of materials, viz. the powers 

 of crystalline bodies to sustain pressure for an indefinite period of time, and 

 to ascertain whether cast iron, when subjected by a given weight to long- 

 continued transverse strain, would, or would not, be subject to fracture. 



It appears that former writers on the transverse strength of materials had 

 come to the conclusion, that the bearing powers of cast iron were confined 

 within the limits of that force which would produce a permanent set, and 

 that it would be unsafe to load this material with more than about one-third 

 of the weight necessary to break it. This assumption is, however, incorrect, 

 as the experiments which follow will abundantly testify. 



It would be superfluous to offer in this notice any observations on a dif- 

 ferent theory, as the recent experiments of Mr. Hodgkinson and myself fully 

 prove* that cast iron takes a permanent set with a load considerably under 

 one-sixth of the breaking weight. 



From these experiments, it will be found that cast iron is more to be de- 

 pended upon, and exhibits more tenacity in resisting heavy strains long con- 

 tinued, than is generally admitted, and its bearing powers have deserved a 

 much higher reputation than has at any former period been given to them : 

 indeed it is evident from the experiments, that a cast-iron bar is capable of 

 resisting for a series of years a force equal to §ths, and sometimes ^yths of 

 the load that would break it. 



In the application of this force, it must be observed, that the room in 

 which the experiments were made, and which are now in progress, is not 

 entirely free from vibration, being slightly affected by persons crossing the 

 floor, particularly when two or more are walking at the same time. 



The experiments already published on the " Effects of Time," embrace a 

 period of fifteen months, from the 6th of March 1837 to the 23rd of June 

 1838. Up to that time the deflections of both hot and cold blast iron were 

 carefully registered ; and the present is a continuation of the same experi- 

 ments, exhibiting the changes that have taken place for the last four years, 

 and the effects which the permanent weights have produced upon the bars. 

 It is satisfactory to observe that, during the whole time of the experiments, 

 the bars (whether loaded with the lighter or heavier weights) exhibited little 

 or no change beyond what may be traced to the variations of temperature. 

 One of the bars was, however, found broken some time since, but whether 

 from accident or the effects of continued strain I am unable to determine with 

 certainty ; I am inclined to believe that the former was the cause, as the cor- 

 responding bars still retain their position, indicating changes so exceedingly 



* See Reports on the Strength and other Properties of Cast Iron in the seventh volume 

 of the Transactions of the British Association, and the sixth volume of the Manchester 

 Memoirs. 



