National Geographic : 1942 Jan
The National Geographic Magazine SV Fred Masters Unloading and Chopping Kelp, Which Makes Ice Cream Easier to Swallow! From about 150 square miles of kelp beds offshore near San Diego, big seagoing lawn mowers cut the weed (page 65). It yields not only solvents and minerals, but algin, used in making ice cream; also certain vitamins in poultry foods and in fox food served on some fur farms. Potash and iodine are recoverable from kelp, and so is agar, known to Malays as agar-agar.