Wrltten lor tlio Courier. Pen ris are regarded by a large claas of wealthy and refined people with ncarly as much favor as diamond. And as sonie of the readers of the Couuier, may not know that many pearls which pass for genuine, are produced by artlïkial means- or rather thelr formation induced in an unnatural way- a few remarks on the subject will not be out of place in on ai ticle about shells, and their manufacture; especially as the Mothcr of Pearl, in which the genuine pearl is chielly found- also artiücially produced -is one of the most important and valuable of the shell species. The basis or nucleus of the genuine pearl is generally a small, hard, foreign substance that has found lts way into the Shell of the Mother of Pearl. Being unable to expelí the intruder, a systeiu of protection is Immediately commenced by covering the last substance all over with pearly layers, thu3 forming a perfectly round, smooth, genuine pearl. Knowing their tendency to completely envelope any intrudiug substance, the Japanese oftentimes force open the Mother of Pearl shells- usually closed rery tightly, and drop small shot inside of theru; most of the sliot are ejected, but if only one iinds a lodgmcnt in the Mother of Pearl, it is sure of causlug the formaation of a pearl in the manncr stated above. SIIELLS. Among several different varieties oí the shell species, Mother of Pearl shells are deserving of first mcntlon. Shey are obtained princlpally from Australia and the East Indies, and vary in size from 8 to 15 inchcs across. Besides being uscd largely for buttous aud scarf pins, for which are well adapted, thcy are extensively cmploycd for pistol handles, table and penknife handles, opera glasses and penholders, as well as belng wrought into a gveat variety of fancy patterns for ornamental and other purposes. Being an excellent non-conductor of heat, and taking a very high polisli, peail is also used extensively for the handles of teakettles and urns. Piano-keyd with pearl tops are very desirable too, as they will neither crack nor warp nor gather dainpness like instrument keys with other materials for tops. In addition tothe purposes euunierated, pearl is employed for non-conductors, and the thiu scales are utilized largely in niaking letters for glass signs, inluying work-boxes, stands, and other expensive furniture, and for leaves and flowers in buttons. Pearl can be dyed or colored any desired simde by treating It with nltrate of silver, and exposing it in the open air to the sun which brings out the color. Thus the great utility of Mothcr of Pearl shells can readily be secn. And sorae idea of their valué may be gained when it is stated that they are worth in the rough, just as they are found, from 50 to 75 cents per pound. Ia a store window in New York City, the writcr noticed, not long ago, one of the largest of this class of shells to be found in the country; its value bcing fully twentyfive dollars. It is wortliy of remark in tliis connection, that the insido and outside of tbis shell is the same in quality and appearance as the genuino pearl, but being formed in layers, it does not look the same where it is cut, and is not as susceptible of receiving a high polish as the other portions of the shell, otlicrn-iae they could be employed in the manufacture of pearl s Tahiti or black shells, mostly obtalned fiom the Phüipine Islunds and the Japan snail, fouiid along the coast of that country, are chiefly used for making colored buttons; different dyes producing a very beautiful effect on these shells. In New Zealand, a class of shell of a bright green color, and known as Apolonia, are found; they vary from four to twelve Inchcs in size, and are largely usecl for painting and various kinds of ornamental work. Deep shells with holes In tliem, also called Apalonla, of which tliere are some ilfly different species, mostly obtained frorn California and along the coast of Japan, are cliieily used for buttons and inlaid work. And besides the vnrieties naraed, tliere are Lake Superior ïnussel shells, used principally for paintings. MANUFACTURE OK SUKLL (JOODS. The manufacturing of shell goods niay be briefly described as follows: The shells are usually tirst cut into strips from four to six inclies long and from lialf an inch to one Inch in width, and ubout a quartcr of an inch In thicknes?. 'l'lir e strips are afterwards ground, to remove the rough portions, on rapidly revolving grind stones, about 36 inclies in diameter, and tlien linislicil and polished on socalled "feit buftV' - wheels made of feit cloth, and which revolve with a velocity of from 1,500 to 5,000 revolutions per minute. Emery wheels are alao employed for sliaping different kinds of shell goods. In making pcarl buttons the blanks nrc lirst sawed with small "tube" saws, and tlien turned in a lutho. Afterwards the holes are pierced witli small drills t luit revolve ut great speed. On account of the varying qunlity and thickness of the strips of pearl, and its worklng being guided by the eye alone, only artisans possessing a high degree of skill and long experience are allowed in the imlustry; the material being too expensive to be unneccssarily wastcd. Gathering shells n varloui p.irts of the world, affords employment to a large number of pereons, and the manufacturing of shells Into many bcautiful and expenslre goods forms quite an Important industry. It has been carried on n England for uearly two centuries, and wns flrst started in tbts country about fifty years ago, yet up to thia time, there are only a few establishments in the United States that carry on the business in all its branclies.