Various, Popular Science Monthly (1914)
“ The curves for whale oil and sperm oil differ in certain important points. Except on the "tails" of the curves the imports of the more valuable sperm oil are far in defect of those for whale oil. Probably in consequence of the greater demand the source was earlier exhausted. The mode of the sperm-oil curve lies, in consequence, nearer the inception of the industry, and the curve is therefore far more skew. It is interesting to note that in more recent years, the imports of sperm oil have been maintained at a relatively higher point than has that of whale oil. ”
