PROCEEDINGS OV THE POLYTECHNIC ASSOCIATION. 601 



BO that a metal will melt, and we can ascertain within ten or 

 fifteen degrees its melting point. Alloys may be made of differ- 

 ent degrees of fusibility in the form of shot, and the melting 

 point of each ascertained. Then in order to measure heat, it 

 will only be necessary to ascertain by trial, that a certain shot 

 will melt, but that the next to it in the scale will not, when ex- 

 posed to that heat. 



DISINFECTION BY CHARCOAL. 



Mr. Johnson exhibited a mummified mouse, the mouse having 

 been buried in charcoal dust two years ago ; and suggested that 

 charcoal should be used in burial cases. 



COTTON AND ITS SUBSTITUTES. 



The Chairman. — I procured samples of the six best cottons, 

 and subjected them to microscopic examination. Their peculi- 

 arities were these : the fiber at first appeared knotted; but more 

 careful examination disclosed that these were bends in the rib- 

 bon, which were fixtures, and had probably occurred in the ri- 

 pening of the fiber. With one exception, it was found that in 

 proportion as the fibers are larger or longer the bends were fur- 

 ther apart. The cotton with the small fiber and infrequent bend, 

 was from Texas, and Avas worth 15 cents per lb., the average be- 

 ing 11 cents. The width of the fiber of the Florida cotton Avas 

 certainly three times that of the Texas cotton. The cottons ap- 

 peared to be good just in proportion as they approached the 

 South sea air. While the width of the cotton fiber varied from 

 l-1200th to l-3000th of an inch, over 300 of these bends were 

 found to the inch. The joints of fine wool proved to be far more 

 numerous than the bends of the cotton, nearly double. In the 

 length of fiber, the cotton from the dest districts was almost uni- 

 form. Cotton is valuable in proportion as its growth is so ma- 

 ture that all the fibers in the boll arc very nearly of the same 

 length ; for then it comes into fair comparison with wool from 

 the same flock of well-kept sheep. 



The object of spinning-machinery is to straigliten the fibers, to 

 cleanse them, and get them into such a relation to each other 

 that they will draw a twist evenly ; and the same force being 

 constantly applied, the more uniform the length of the fiber, the 

 better it will work. At least nineteen-twentieths of the value of 

 our cotton fabrics is due to machinery. In 1841, the father of 

 your chairman, who had established the first cotton factory in 



