4 Trans. Acad. Sci. of St. Louis. 



The screw head should be soldered or brazed to the second 

 disk, in an air-tight joint. The screw threads are held in a 

 perforated nut brazed into the end of the tube.* Between the 

 disks is clamped a circular, porous layer, which extends half 

 an inch or more outside of the metal disks. The material 

 best suited to use in this porous layer seems to be wire screen . 

 I have tried the finest brass wire cloth, having 130 wires to 

 the lineal inch, and ordinary iron window screen, having 12 

 wires to the inch. The number of thicknesses of screen has 

 been varied from two to twelve. The results were not 

 appreciably affected by such changes. For use in rain storms 

 the coarse iron wire is to be preferred. Three sheets of wire 

 screen, making angles of 30° with adjoining sheets, give very 



"^■^'V^^ ' 



Fig. 1. 



satisfactory results. The wire may be dipped into a thin oil, 

 in order to prevent water from clogging the layer. When the 

 fine wire is used, the central part of the layer around the 

 screw should be punched out to form an air chamber. 



According to the plan which dictated the design of the col- 

 lector, it was to be unaffected by wind, when placed edge- 

 wise in the air current. The air currents between the two 

 disks are so checked that no atomizer action is possible. The 

 compression on the windward edge of the porous layer, is 

 dissipated by lateral outflow before it penetrates between the 

 metal disks. The rarefaction on the leeward edge is similarly 

 prevented from affecting the air between the disks. This is 

 accomplished by a lateral inflow of air. The arrows in Fig. 

 1, roughly indicate the action described. This collector was 

 placed under a bell-jar resting on a glass plate. The tube led 



♦ Soldered joints will serve unless the collector is to be used in the hot 

 air of a chimney. 



