14S Dr Jones on Polishing Ivory ^ S^e. 



Horn and Tor'toise-sheU. 



These substances are so similar in their nature and texture, 

 that they may be classed together^ as far as regards the general 

 mode of working and polishing them. A very perfect surface 

 is given by scraping them ; the scraper may be made of a razor- 

 blade, the edge of which should be rubbed upon an oil-stone, 

 holding the blade nearly upright all the while, so as to form an 

 edge like that of a currier's knife ; and which, like it, may be 

 sharpened and improved by burnishing, at least so far as its 

 hardness will permit. 



To prepare the work, when properly scraped, for polishing, 

 it is first to be rubbed with biiff', made of woollen cloth, per- 

 fectly free from grease ; the cloth may be affixed upon a flat 

 stick, to be used by hand, but what workman call a hob, which 

 is a wheel running in the lathe, and covered with the cloth, 

 either upon its edge or periphery, or flat face, as may be requir- 

 ed, is much to be preferred, on account of the rapidity of its 

 operation. This buff" or bob is to be covered either with pow- 

 dered charcoal and, water, or fine brick dust and water. After 

 the work has been made as smooth as possible by this means, it 

 must be followed by another buff* or bob, on which washed 

 chalk or dry whiting is rubbed ; the comb, or other article, is to 

 be slightly moistened with vinegar, and the buff^ and whiting 

 will produce a fine gloss, which may be completed by rubbing- 

 it with the palm of the hand, and a small portion of dry whit- 

 ing or rotten stone. — FranMin Journal. 



Abstracts and Remarks relative to Captain Sabine'^s Expei'i- 

 ments on the Dip and Intensity of' the Magnetic Needle, in 

 different parts of the Northern Hemisphere. By Peter 

 Barlow, F. R. S., Mem. Imp. Ac. Petrop. Communica- 

 ted by the Author. 



Xn my former paper relative to the magnetic experiments 

 made during the late Northern Expedition *, I endeavoured to 



• I wish here to correct an omission in the title of my former paper. It was 

 intended that the experiments should have been stated to have been " By Captain 

 Parry, Lieutenant Foster, and the other Officers of the Expedition." 



