trial balloon

For many weeks in succession the little trial balloons thrown up to show the course of the wind were driven back upon the shores of France.

"The originality of the plan and views of the author [Jean Baptiste Bory de Saint-Vincent], and, above all, the perfect independence of its execution," are, according to the narrator in the Bulletin, the chief features of this new production; and the summary sketch of it which has been published, is (to use the phraseology of the same writer) "as a kind of trial balloon," launched with the view of seeing how the wind sits for his "great work."