appearances as to width, intensity, and arrangement of the two stripes; also in some cases the direction of the lines may vary, although by the smallest quantity, but still deviating by a small amount from the canal with which they are directly associated.  From this important fact it is immediately understood that the gemination cannot be a fixed formation upon the surface of Mars and of a geographical character like the canals.  The second of our maps will give an approximate idea of the appearance which these singular formations present.  It contains all the geminations observed since 1882 up to the present time.  In examining it it is necessary to bear in mind that not all of these appearances were simultaneous, and consequently that the map does not represent the condition of Mars at any given period; it is only a sort of topographical register of the observations made of this phenomenon at different times.[D]

The observation of the gemination is one of the greatest difficulty, and can only be made by an eye well practiced in such work, added to a telescope of accurate construction and of great power.  This explains why it is that it was not seen before 1882.  In the ten years that have transpired since that time, it has been seen and described at eight or ten observatories.  Nevertheless, some still deny that these phenomena are real, and tax with illusion (or even imposture) those who declare that they have observed it.

Their singular aspect, and their being drawn with absolute geometrical precision, as if they were the work of rule or compass, has led some to see in them the work of intelligent beings, inhabitants of the planet.  I am very careful not to combat this supposition, which includes nothing impossible. (Io mi guarderò bene dal combattere questa supposizione, la quale nulla include d’impossibile.) But it will be noticed that in any case the gemination cannot be a work of permanent character, it being certain that in a given instance it may change its appearance and dimensions from one season to another.  If we should assume such a work, a certain variability would not be excluded from it; for example, extensive agricultural labor and irrigation upon a large scale.  Let us add, further, that the intervention of intelligent beings might explain the geometrical appearance of the gemination, but it is not at all necessary for such a purpose.  The geometry of nature is manifested in many other facts from which are excluded the idea of any artificial labor whatever.  The perfect spheroids of the heavenly bodies and the ring of Saturn were not constructed in a turning lathe, and not with compasses has Iris described within the clouds her beautiful and regular arch.  And what shall we say of the infinite variety of those exquisite and regular polyhedrons in which the world of crystals is so rich?  In the organic world, also, is not that geometry most wonderful which presides over the distribution of the foliage upon certain plants, which