THE NATIONAL PHYSICAL LABORATORY. 139 



nickel steel with its small coefficient of expansion appears to have a 

 future for many purposes; can it by some modification be made still 

 more useful to the engineer ? 



"We owe much to the work of the Alloys Eesearch Committee of the 

 Institution of Mechanical Engineers. Their distinguished chairman 

 takes the view that the work of that committee has only begun and that 

 there is scope for research for a long time to come at the National Phys- 

 ical Laboratory, and the executive committee have accepted this view by 

 naming as one of the first subjects to be investigated the connection be- 

 tween the magnetic quality and the physical, chemical and electrical 

 properties of iron and its alloys with a view specially to the determina- 

 tion of the conditions for low hysteresis and non-aging properties. 



At any rate we may trust that the condition of affairs mentioned by 

 Mr. Hadfield in his evidence before Lord Eayleigh's commission which 

 led a user of English steel to specify that before the steel could be 

 accepted it must be stamped at the Reichsanstalt will no longer exist. 



The subject of wind pressure again is one which has occupied the 

 committee's attention to some extent. 



The Board of Trade rules require for bridges and similar struc- 

 tures (1) that a maximum pressure of 56 pounds per square foot be 

 provided for, (2) that the effective surface on which the wind acts 

 should be assumed as from once to twice the area of the front surface 

 according to the extent of the openings in the lattice girders, (3) that 

 a factor of safety of 4 for the iron work and of 2 for the whole bridge 

 overturning be assumed. These recommendations were not based on 

 any special experiments. The question had been investigated in part 

 bv the late Sir Wm. Siemens. 



During the construction of the Forth Bridge Sir B. Baker con- 

 ducted a series of observations. 



The results of the first two years' observations are shown in Table 

 II. taken from a paper read at the British Association in 1884. Three 



