36 Journal of the Mitchell Society [August 



this suite terminates or is periodic. It is found that a necessary and 

 sufficient condition that the flecnode suite terminate with its first 

 transform is that the given ruled surface have a straight line directrix. 

 The equations of the most general curve which can serve as the 

 second branch of the flecnode curve of a ruled surface with a straight 

 line directrix can be obtained without integration. A necessary and 

 sufficient condition that the flecnode suite terminate with its second 

 transform is determined. It turns out to be the vanishing of an in- 

 variant of weight thirty. The equations of both branches of the 

 flecnode curve on a ruled surface may be determined without integra- 

 tion if the flecnode suite terminates with its second transform. The 

 flecnode suite is of period two, when, and only when, the flecnode 

 curve meets every generator in two coincident points, or is inde- 

 terminate. The flecnode suite cannot be of period three, nor of 

 period four. 



A. H. Patterson — A Netv Process of Lead Coating. 



Secretary Hoover is quoted as saying that next to the fire loss in 

 this country is the rust loss. Many methods are employed to protect 

 surfaces — electroplating, dipping, varnishing, painting, etc. All of 

 these methods are unsatisfactory for one reason or another, expense 

 or otherwise. The new method was described as a process of coating 

 metals with lead. As the process is a secret one, no details could be 

 given, but samples were submitted showing the results. One inter- 

 esting thing about the process is that the lead seems to form an alloy 

 with the metal on which the coating is laid. For this reason the trade 

 name of the process is Intraloy. As far as could be done Avith pro- 

 priety. Professor Patterson described the tests made on this process 

 last summer while he was in the employ of the company that is de- 

 veloping this process. The process bids fair to be of immense use- 

 fulness. 



263rd Meeting— February 12, 1923 



John D. Capron — The New de Lavaud Method of Making Cast Iron 

 Pipes hy a Centrifugal Process. (By invitation). 



Mr. Capron, of the United States Cast Iron Pipe and Foundry 

 Company, presented an interesting and instructive talk on the new 

 de Lavaud method of making cast iron pipes by a centrifugal pro- 



