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X PREFACE TO THE placed, according to the system of notation adopted in the “ Fa miliar Introduction to Crystallography, &c. by II. J. Brooke, F. R. S. &c.” a work which may, without hesitation, be recom mended strongly to the student, as being calculated to teach the interesting science on which it treats in its most pleasing form, and of which the first part is so simple that, without any re- i\, ference to trigonometry, geometry, or algebraical calculation, it shows, by means of the figures of crystals and attendant explana tions, the position on the primary forms of every secondary or modifying plane to which those forms are liable, and thereby the transitions of one form into another; and here, if he be so in clined, the student may stop, after having gained all that a purely mechanical view of the subject will afford him, or he may proceed to the second part, in which crystallography is treated more scientifically; and it may be added, that the pupil may, in either case, attain such a knowledge of it, as will not fail to open to him new sources of delight in this interesting department of Mineralogy. To the author of the fore-mentioned work I am under much obligation, for assistance on various points connected with the improvements which it is confidently hoped will be manifest in the present Edition. Often as his name occurs in its pages, I have been yet more often indebted to him, not only for the loan of specimens, amongst which were several that I could not other wise have obtained, but for assistance in the clearing up of many difficulties which, without his help, would have been left in doubt, or would have terminated in error. My acknowledgments and thanks arc also thus publicly due to several others of my friends. To Thomas Allan, I'.lt.S.L. & E. for many useful criticisms, of which I have not failed to avail myself, as well as for the liberal transmission from Edinburgh of some rare and valuable minerals. To Ashlmrst Majendie, M.G.S. for the loan of well-defined crystals of several scarce sub stances. To Samuel Luck Kent, M. G. S. for a free access to his cabinet upon all occasions, and for his cheerful permission to avail myself of the advantage in any manner that might tend to benefit the work, and even for the presentation to me of some rare substances. To Ilenry Ilculand, For. Sec. G. S. for some valuable minerals presented to me in a manner consistent with s his well-known liberality; a liberality which also I have exper ienced in numerous instances from G. 15. Sowerby, F. L. S. to whom likewise I am greatly indebted for many valuable hints, and for the readiness with which lie has upon all occasions cn- * deavoured to promote my views. In conclusion, if the utility of a nice investigation of the structure of crystallized minerals, and the measurement of their angles, should become an inquiry, it may be replied that they f