Air Machines—From Decaus.

SSO

[Book IV.

water to flow out as in the figure. And after the heat of the day is pass-ed and the night shall come, the vessels shall draw the water of thecistern [spring] by the pipe and sucker [lower valve] and shall fill the

vessels as before. .- And you must observe that the two

suckers [valves] must be made very light and likewise very just, so asthe water may not descend by them after it is raised.”

No. 174. Air Machine, from Decaus.

An improvement upon the preceding machine is next given by Decaus.The form of the vessels is altered, and double convex lenses or “ burningglasses” are so arranged on their covers as to collect “ the raies ofthe sun within the said vessels, the which will cause a great heatto the water, and by that means make it spring forth with great abun-dance, and also higher if it be required.” (See the figure below.) It is,we think, in the ränge of probability that the heat of the solar rays majyet be applied in soijje situations to raise water with effect

No. 175. Air Engine, from Decaus.

Whether this application of lenses “ to encrease the force of the sun”in air engines, was a device of Decaus, we know not. The idea however