804 



REPORT 1888, 



The figures seem to show that when the lowest level is reached, continuance of 

 rainless periods has not much effect on the river. But, besides the mere absence 

 of rain, so many other matters have to be taken into account that a deduction is 

 impossible. 



SATURDAY, SEPTEMBER 8. 



The following Papers were read : — 



I. On Rolling Seamless Tithes from Solid Bars or Ingots, by the Mannesmann 

 Process.^ By Frederick Siemens. 



The author refers to the circumstance that steel and toughened glass, though 

 specially suitable, on account of their high qualities and strength, for use in the 

 arts, have been somewhat neglected owing to the difficulty of welding and cutting 

 them. Attention is next drawn to the combination of strength with lightness 

 which the tubular form admits of, and to the extensive use of tubes in construction 

 which is likely to follow from a simple means of producing them. The different 

 kinds of rolls hitherto employed which are classed as the longitudinal, circular and 

 intermediate, are passed in review, and the process which forms the subject of the 

 paper is then described. 



In the Mannesmann Process, a certain relation between longitudinal and rotary 

 motion is maintained, so adjusted for each material to be worked that a twist is 

 imparted to the fibre resulting in great strength and toughness of the manufactured 

 product. The following is the mode of manufacture : A bar is placed between 

 conoidal rolls, where the diameter and therefore the velocity are least, and 

 is gradually drawn forward into contact with those portions of the rolls which 

 travel more and more rapidly. The rolls are so set that the space left between 

 them for the passage of the bar decreases slightly, so as to cause a certain amount 

 of material to be shifted. The action of the rolls preventing this material from 

 being taken from the outside of the bar, it is consequently drawn from the interior, 

 a hollow being first produced and then a tube. 



A mandril may be employed to finish and smooth the interior and to enlarge 



' Printed in extenso in Engineering, vol. xlvi. p. 291. 



