Microscopical Physiography Of The Rock-making Minerals - An Aid To The Microscopical Study Of Rocks

Microscopical Physiography Of The Rock-Making Minerals: An Aid To The Microscopical Study Of Rocks - 1888 - TRANSLATORS PREFACE - IN peparing an English translation and abridgment of Professor osenbuschs Mikroskopi heP hysiographie dbr petrographiscll wicl tigen Mineralien, with his permission, it has been my desire to present to English-speaki lgs tudents the essential features of this valuable work, which contains all that is necessar, y for an accurate and COIII plete deterlnination of the rock-making minerals hoping that in so doir g I may not only meet tEe wants of those who take up unaided the study of rocks, but may assist those who are teaching this impor tant bran cl of geology by providing them with a reference-book COII taining the diagnostic characters of these minerals. It is also hoped - that it Inay lead - to a more general interest in and a more accurate knowledge of rnicroscopical petrography in this country, and ma . r I increase the number of those vho b, y exaet and patient study, shall add to the store of established PaGks, and . thus advance the science of lithology. In abridging the book, I have endeavored to retain all that appeared to be essential to a fair, general cornprei ension of the - srtb-ject, omitting what seemed to be refinements beyond the need of the average student, and for which the advanced student is referred to the original work. Thus most of the llistorical portions 11ave been omit ted, as well as the elaborate treatment of the optical nnornalies of cer tain minerals, and many notes on European localities while a number of notes on Arnerican occurrences have been inserted. In two instances I have take11 the liberty of depiirting froln theoriginal in the use of nalnes, the grrourlds for whicl Professor Rosen busch mill undoubtedlv appreciate. The term SyZiirob. ysta8 1x1s bee11 rendered qheru ite, as the latter has becon e well established in English petibgraphical literature, ancl is not open to the objectiorl vllich might be raised against the new term. L a ite has been rendered hyozite a, lso for the reason that it is in such general use in this country and in England that to supplant itt mould lend to great con fusion. With these exceptions I trust Professor Rosenbusch may find vi TOR WORT. Bedeutllng gerade der oytiscllen Eigenscl aften fur die Erkennung der Jfineralien unter dem Dlikroskope und die oft gemachte El-fallrung, vie sehr dieselben von den Studirenden zu ihrem eigenen griissten Schaden ver acl liisswigetr deu. Allenthalben, wo es niithig schiel, habe ich die besprochenen Verhiiltnisse durch schematische Zeiclrnungen zu erliilltern geaucht dieselben sollen nur die Anschauung erleicl tern und rnachen auf sti8enge Winkelgenauigkeit keinen Ansprucl. - Die ganze Anlage und der Zweck des Buclles, welches ja kein Lehrbl ch der Mineral-Optik s e i so ll, diirften es ivohl hinreichend erkliii-en, dass nicht eine stre igere Form fur die Besprec hu ng d ieser VerhWltnisse gelviihlt wurde. Aehnliche piidagogische Erwiigigungen leiteten rni auch, wenn ich z. B. die Er liiuterur gd er optischen Erscl einungeni n diinnen, doppeltbrechenden 3Iinerallamellen irn polarisirteu Liichte del Erkliirling der gleichen Phanome le in dickeren Krystallplatten vorausgeheri liess, obwohl ja die im ersten Fall anftretenden Farben nur der centrale Tlleil des Bildes sind, welches wirirn zweiten Fall erhalten...