950 Transactions of the American Institute. 



In relation to the item on " Black Paint," Dr. Vanderwe3''de 

 remarked that he preferred a yellow color for the dark room for 

 photographic purposes, as black makes the room too dark. 



Dr. Bradley stated that sweet milk mixed with red ochre makes 

 a good pamt for country houses and barns. 



NEW TYPE-WRITING MACHINE. 

 Mr. John Pratt, of Alabama, exhibited his type-^i-iting machine. 

 It was intended to dispense with a great deal of hand-writing, and 

 to have an apparatus which can be emfployed quickly and reliably, 

 not only by business men, but also by all those who cannot employ 

 the pen rapidly. With this machine he claimed a person could, 

 without any practice, write about as fast as with the pen, that is, 

 about thirty words a minute. The printing is done on carbonized 

 paper, by simply striking a few keys, much like those of a piano-forte. 

 With a knowledge of the arrangement of the keys, an operator can 

 print with almost as much rapidity in the dark a.s by light. By an 

 automatic movement, the paper, which hangs verticall}^, is moved 

 at the completion of every line into a proper position for printing 

 the next line. There are only fifteen keys for the whole alphabet. 

 The machine can be made for five or six dollars. When constructed 

 on a large scale, four or five copies can be taken at the same time. 

 This was the first time this machine was exhibited in public. 



LOW WATER DETECTOR FOR BOILERS. 



Brown's low water detector was next exhibited. It consists of 

 a brass tube connected with a metallic bar, which does not expand 

 as much by the application of the same amount of heat. These 

 are inserted vertically into the boiler, and connected with a lever 

 on the outside, which is moved by any difiereuce of expansion 

 between the bar and the tube. When the water is too low, steam 

 enters the l)rass tube and expands it, which causes the lever to open 

 a valve, the steam in escaping blows a whistle, and thus gives the 

 alarm. 



PARALLEL RULER. ' 



Prof. C. A. Joy exhibited an ingenious parallel ruler, recently 

 brought from Paris by him. It was designed for drafting purposes, 

 to lighten the labors of draftsmen in drawing section lines. This 

 machine is specially adapted for engravers, as it makes very fine 

 parallel lines, of great length. 



