THIS paper is written principally with the hope that it will induce other members to follow with other papers on the various indications of ore deposits which may have come under their notice, whether the indication consists of a peculiarly coloured outcrop or in a change in the nature of the country rock, or in whatever it may be.In many, in fact, in most cases, it is exceedingly difficult to state what is really an indication of an ore deposit. What are often spoken as indications may sometimes be so, and yet at others they may have no value whatever. What may be considered as an almost certain indication of an ore deposit in one district may not hold good in another. The experience gained in one district can only be used with the greatest caution and constant consideration in another.What is often considered one of the most usual signs of the presence of an ore deposit is the appearance caused by the decomposition and alteration of the lodes owing to atmospheric action. It is known as Gossan, Iron Hat, Chateazt en Fer, Pecos, Colorados, &c. " In Germany the outcrop or upper portion of many lodes, especially those rich in metallic sulphides, has been called Iron Hat (eiserner Hut) ; the peroxide and hydrated peroxide of iron are formed by the decomposition of sulphides containing a large percentage of iron-iron pyrites, magnetic pyrites, chalcopyrite, mispickel, blende-which, being disseminated through the whole gangue, give a predominant red or brown colour. These masses resemble ironstone and can in some cases be used as such.