notice. In this connection also should be mentioned the " characters," which the diarist Pepys drew up when clerk to Sir George Downing and secretary to the earl of Sand wich and to the Admiralty, and which are frequently mentioned in his journal. Pepys describes one of them as " a great large character," over which he spent much time, but which was at length finished, 25th April 1660 ; " it being," says he, " very handsomely done and a very good
one in itself, but that not truly alphabetical."Shorthand marks and other arbitrary characters have also been largely imported into cryptographic systems to repre sent both letters and words, but more commonly the latter. This plan is said to have been first put into use by the old Roman poet Ennius. It formed the basis of the method of Cicero s freedman, Tiro, who fieems to have systematized the labours of his predecessors. A large quantity of these characters have been engraved in Gruter s Inscriptions. The correspondence of Charlemagne was in part made up of marks of this nature. In Rees s Cyclopaedia specimens were engraved of the cipher used by Cardinal Wolsey at the court of Vienna in 1524, of that used by Sir Thomas Smith at Paris in 1563, and of that of Sir Edward Stafford at Madrid in 1586 ; in all of which arbitrary marks are introduced. The first English system of shorthand Bright s Characterie, 1588 almost belongs to the same category of ciphers. A favourite system of Charles I., used by him during the year 1646, was one made up of an alphabet of twenty-four letters, which were represented by four simple strokes varied in length, slope, and position. This alphabet is engraved in Olive s Linear System of Shorthand, 1830, having been found amongst the royal manuscripts in the British Museum. An interest attaches to this cipher from the fact that it was employed in the well-known letter addressed by the king to the earl of Glamorgan, in which the former made concessions to the Roman Catholics of Ireland.
Complications have been introduced into ciphers by the employment of " dummy " letters, " nulls and insignifi- cants," as Bacon terms them. Other devices have been introduced to perplex the decipherer, such as spelling words backwards, making false divisions between words, <tc. The greatest security against the decipherer has been found in the use of elaborate tables of letters, arranged in the form of the multiplication table, the message being constructed by the aid of preconcerted key-words. Details of the working of these ciphers may be found in the treatises named in this article. The deciphering of them is one of the most difficult of tasks. A method of this kind is ex plained in the Latin and English lives of Dr John Barwick, whose correspondence with Hyde, afterwards earl of Clarendon, was carried on in cryptography. In a letter dated 20th February 1659-60, Hyde, alluding to the skill of his political opponents in deciphering, says that " nobody needs to fear them, if they write carefully in good cyphers." In his next he allays his correspondent s apprehensiveness as to the deciphering of their letters.
"I confess to you, as I am sure no copy could be gotten of any of my cyphers from hence, so I did not think it probable that they could be got on your side the water. But I was as confident, till you tell me you believe it, that the devil himself cannot de- cypher a letter that is well written, or find that 100 stands for Sir H. Vane. I have heard of many of the pretenders to that skill, and have spoken with some of them, but have found them all to be mountebanks ; nor did I ever hear that more of the King s letters that were found at Kaseby, than those which they found decyphered, or found the cyphers in which they were writ, were decyphered. And I very well remember that in the volume they published there was much left in cypher which could not be understood, and which I believe they would have explained if it had been in their power."
An excellent modification of the key-word principle was constructed by the late Admiral Sir Francis Beaufort ; it has been recently published in view of its adaptation to telegrams and post-cards.
Ciphers have been constructed on the principle of alter ing the places of the letters without changing their powers. The message is first written Chinese-wise, upward and downward, and the letters are then combined in given rows from left to right. In the celebrated cipher used by the earl of Argyle when plotting against James II, he altered the positions of the words. Sentences of an indifferent nature were constructed, but the real meaning of the message was to be gathered from words placed at certain intervals. This method, which is connected with the name of Cardan, is sometimes called the trellis or cardboard cipher.
The wheel-cipher, which is an Italian invention, the string- cipher, the circle-cipher, and many others are fully explained, with the necessary diagrams, in the authorities named above, more particularly by Kliiber in his Krypto- graphik.
CRYSTALLOGRAPHY. When water containing saline matter in solution is allowed to evaporate slowly, the salt it contains is thrown down in bodies of peculiar forms, bounded by smooth, even surfaces meeting in straight lines. Fused metals consolidating in certain favourable conditions appear as similar bodies. And in nature also, in cracks or fissures of the rocks, or imbedded in their mass, minerals resembling these in form are frequently found. These regular polyhedric, or many-sided Definition bodies, whether natural or artificial, are named crystals, of crystal and the science naming and describing the forms they assume, and pointing out the relations that exist among them, is termed crystallography. In a theoretical point of view this science may be regarded as a branch of mathematics, and might be studied independent altogether of the fact of any material bodies existing in the forms described. Practically, however, its chief interest and value is as a mean of distinguishing many salts, ores, and other substances, either formed artificially or, more especially, occurring naturally as minerals. At present no particular system of crystallography has found general acceptance, and referring for the details of the one adopted in the description of mineral species to Mineralogy, we propose in this place to give an account of the history of the science, pointing out the more remarkable steps in its progress, the chief general results attained, and some of the best works from which further information in regard to it may be obtained.
The term crystal, found in most modern European languages, is derived from the Greek word [ Greek text ], meaning ice or frozen water, and subsequently transferred to pure transparent stones cut into seals, and, as was thought, only produced in the extreme cold of the lofty passes of the Alps. Pliny, who notices this rock-crystal in his Natural History (book xxxvii.), points out clearly enough the hexagonal form of the crystals, remarking that it is not easy to give any reason why they grow in this foim, mere especially as the points have not the same appearance (<o magis quod ticque muironibus (adcni species tst), ard ll.e polish of the sides is such that no art can equal it. Tl e forms of other minerals are ako noticed by him, but the term crystal still had icgard to the ice-like transparency and purity of the stone, a reference entirely lost in the modern scientific use of the word.
for the beauty of their forms, colours, and other physical properties, attracted considerable attention even in the so-called dark ages. But these notices rather amuse us by their quaint absurdity, as we should now regard it, than throw light on the progress of the science. Thus Albertus
Magnus in the middle of the 13th century tells how the