252 The Commercial Products of the Sea. 



macerated sounds between feed and compressing rollers, by 

 which the viscid substance is compressed and joined, and 

 formed into a continuous sheet. Notwithstanding the con- 

 stant injection of cold water into the rolls, the substance 

 adheres tenaciously to the roll, accumulates thereupon, and 

 has to be cut away; so that the operation is slow and 

 laborious, and productive of imperfect sheets. 



Mr. James Manning, of Rockport, Massachusetts, has 

 invented an improvement, designed to so strip the gela- 

 tinous substance from the rolls that the work may proceed 

 continuously, the ribbon, as it is stopped, being again fed 

 or guided by the operator into and between the rolls until 

 sufficiently reduced or elongated for removal, or, for the 

 action of other rolls, set nearer together to produce a 

 thinner ribbon. He effects this result by placing at the 

 side of each roll a scraper extending the whole length of 

 the roll, having an edge set up to the roll, so that the roll 

 shall run just clear of it, which scraper or cleaner strips 

 from the whole surface of the roll the adhering gelatine in 

 the form of a sheet. 



Knowing that the sturgeon abounded in the North 

 American rivers, and struck by the absence of isinglass 

 from that quarter, in 1851 Professor Owen drew the atten- 

 tion of the Canadian Commissioner to the fact, and now a 

 commerce has sprung up for this valuable product, which, 

 previous to the first London Exhibition, had been rejected 

 among the useless entrails of the sturgeon. Now some 

 attention has been given to the preparation of the air- 

 bladder and the outer tunic of the alimentary canal, after 

 the modes of obtaining the best Russian isinglass. 



The sturgeon enters the rivers of North America, such 

 as the Potomac, Delaware, Hudson, and Kennebec, in 

 numberless quantities, like the shad and herring ; but 



