PATENTS. 



741 



long advocated perforated glass for the better 

 ventilation of hospitals, or indeed of uny rooms, 

 but the difficulty of manufacturing it has hith- 

 erto stood in the way. This difficulty has now 

 been overcome, and glass is made with cir- 

 cular openings of three mm. diameter, spaced 

 fifteen mm. from axis to axis. This gives 5,000 

 apertures to the square metre. The openings, 

 as shown in the diagram, are made 

 flaring, with the small opening 

 outward, which causes the incom- 

 ing currents of air to separate on 

 entering the room, as indicated in 

 the cross-section. It is said that 

 no troublesome draught is percep- 

 tible when the upper panes of a 

 window are fitted with this glass, 

 and whatever outward draught 

 there may be is concentrated by 

 the funnel-like shape of the aper- 

 ture. Such glass in the windows 

 of crowded lecture-rooms would 

 no doubt greatly increase the com- 

 fort of the audience. The small 

 circular marks in the illustration 

 indicate the perforations. The 

 arrows in the sectional view indi- 

 cate the distributing effect of the 

 flaring aperture upon incoming cur- 

 rents of air. 



Me Adams Fins. Such is the singu- 

 lar but appropriate name given by 

 its inventor, John MoAdams, to a 

 device for instantly checking the 

 headway of steamboats or other 

 vessels. During the summer of 

 1886 it was in use on the steamer 

 " Florence," in New York Harbor, 

 and was tested under various con- 

 ditions and with highly satisfactory results. 

 The illustration shows the principle of the at- 

 tachment, namely, two stout doors hinged one 

 on each side of the stern-post of the vessel. 

 Part of the fin is cut away in the drawing, to 

 show the spring that serves to start it outward 

 on being released. The four chains shown lead 

 through dead-eyes into a water-tight chamber, 

 and thence upward over a sheave to a large 

 spiral spring that cushions the strain when 

 the resistance of the water is felt. It will be 

 readily understood that, if the fins are re- 

 leased when the vessel is under way, the 

 pressure of the water will force them out- 

 ward until stopped by the chains, when their 

 entire surface offers itself to check further 

 headway. The invention was thoroughly test- 

 ed by a board of naval officers in August, 

 1886, and their report certifies that the 

 "Florence," when under full headway, was 

 stopped and moved astern in twelve seconds 

 and within a space of about thirty-five feet. 

 There is no doubt that when kept in working 

 order the McAdams fins are highly efficient 

 as a marine brake, and would, if generally 

 adopted, prevent many collisions. The fins 

 are also readily available as auxiliary rudders 



in case of necessity, enabling the vessel to 

 turn far more quickly than is possible with 

 her ordinary steering-gear. 



Photographic Washer. The accompanying 

 drawing illustrates an apparatus devised by 

 M. Gorcieux for automatically washing pho- 

 tographic negatives. A trough, the longitudi- 

 nal section of which is nearly diamond-shaped, 



M'ADAHS PINS. 



is divided in the middle by a partition, and 

 provided with pivots on its outer sides, which 

 are only a little above the center of gravity. 

 These pivots rest in uprights, so that the 

 double trough can oscillate freely, seesaw- 

 fashion. Immediately over the center of oscil- 

 lation is a faucet or appliance to deliver water 

 in a small stream. When the trough is tilted 



PHOTOGRAPHIC WASHER. 



one way, the stream will fall on the upper side 

 of the partition ; and, as soon as the weight of 

 water preponderates on that side, the trough 

 will tilt, bringing the other and nearly empty 

 compartment under the faucet. Thus a rock- 

 ing motion is given to the trough, and kept 

 up as long as the stream flows. The whole 

 affair is set in another trough with a waste 



