With cast iron pipe this cannot be done, and no length of piping over 40 ft.
It is a mistake to stint the quantity of piping, since it is far more economical and better for the plants to have a larger surface heated moderately than a smaller surface heated excessively.
In the United States the danger of the stoves that used to be employed for heating the interiors of the cars has been realized, and now the most common method is by steam taken from the locomotive boiler and circulated through the train in a line of piping, rendered continuous between the cars by flexible coupling-hose.
Of late years a considerable amount of seamless tubing has been made, much in the same way as lead piping, by forcing the mixed rubber through a die, and curing as above.
Later, the serendipitous drippings were augmented by additional piping, carrying excess water to spray even more surface of the rock walls.