INDEPENDENT SHADOWS

Te Aroha News, Volume XLI, Issue 6573, 7 February 1925, Page 7

INDEPENDENT SHADOWS

ACROSS THE SURFACE OF PETROLEUM • Freak shadows that do not fade away at once when the objects that cast them are removed are described by S. Leonard Batsin in St. Nicholas (New York). We read: “In the great oil regions of California, pools of crude petroleum are commonly seen. Here the oil is allowed to remain until it is stored away in barrels. One of the curiosities of the district is the freak shadows which these ponds of crude oil produce. If when the sun is shining brightly a person stands so that his shadow falls across the surface of the petroleum, a remarkable thing happens. Should the individual change his place, strange to say the first shadow remains on the oil, while the pfirson casts a second shadow from his new position. The longer the individual has been standing by the oil pond the longer will his original shadow remain. The explanation of the mystery is simple. Under the influence of the hot sun gas is freely produced in the crude oil. This rises to the • surface in the form of millions of bubbles far too minute to be noticed by the human eye. When a shadow is cast over the surface of the petroleum, the temperature is reduced, and this has the effect of checking the production of bubbles. The result is that the shaded area looks different from the part which is exposed to the sun. Now, when the person moves, the temperature of the oil which has been shielded from the sun does not at once get back to its former warmth. It takes a little time to heat, and until this actually happens the shadow effect persists, giving the curious appearance which has been described.”