The following excerpt is from the November 12, 1892, edition of “Golden Days” magazine. It explains how condensed milk was made: The process very simple, the fresh milk is put into a great copper tank with a steam jacket. It is heated and sugar is added. The mixture is then moved into a vacuum tank, where evaporation is produced by heat.

The vacuum tank will hold approximately nine thousand quarts. It has a glass window at the top, through which the operator in charge monitors it. He can tell by the appearance of the milk when to shut off the steam. This must be done at just the right moment or else the batch will be spoiled.

Next, the condensed milk is drawn into forty-quart cans, set in very cold spring water to revolve rapidly by a mechanism so that the contents may cool evenly.

Ice is put into the milk to bring it down to the proper temperature if it is not cold enough. Finally, the market sized tin cans are filled with the milk by a machine, which automatically pours exactly sixteen ounces of milk. There is a worker placing the cans beneath the spout while another worker removes them once they are filled.

Which text feature would be most helpful for the reader to understand the process of making condensed milk?