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Apparatus for forming artificial thermals for sail-plane use which comprises in combination a black body positioned to permit solar rays 3' to impinge thereon to heat said body and in turn to heat adjacent atmosphere thereby causing it to ascend, vertically positioned adjustable guide means pivotally mounted adjacent the periphery of said body for imparting an angular momentum 55 to said ascending air current or thermal, and electrically-actuated means https://www.freepatentsonline.com/2371629.html
www.freepatentsonline.comMeans for producing artificial thermals - Lee, Frederick W.The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon in accordance with