At a distance, one would say that such a spot marked some terrible scene of blood, but, as you come nearer, the hues are so tender and delicate, as they fade from deep red to rose, and so die into the pure colorless snow around, that the first impression is completely dispelled.  This red snow is an organic growth, a plant springing up in such abundance that it colors extensive surfaces, just as the microscopic plants dye our pools with green in the spring.  It is an Alga well known in the Arctics, where it forms wide fields in the summer.  With the above facts before us concerning the materials of which glaciers are composed, we may now proceed to consider their structure more fully in connection with their movements and the effects they produce on the surfaces over which they extend.  It has already been stated that the ice of the glaciers has not the same appearance everywhere, but differs according to the level at which it stands.  In consequence of this we distinguish three very distinct regions in these frozen fields, the uppermost of which, upon the sides of the steepest and highest slopes of the mountain-ridges, consists chiefly of layers of snow piled one above another by the successive snowfalls of the colder seasons, and which would remain in uniform superposition but for the change to which they are subjected in consequence of a gradual downward movement, causing the mass to descend by slow degrees, while new accumulations in the higher regions annually replace the snow which has been thus removed to an inferior level.  We shall consider hereafter the process by which this change of position is brought about.  For the present it is sufficient to state that such a transfer, by which a balance is preserved in the distribution of the snow, takes place in all glaciers, so that, instead of increasing indefinitely in the upper regions, where on account of the extreme cold there is little melting, they permanently preserve about the same thickness, being yearly reduced by their downward motion in a proportion equal to their annual increase by fresh additions of snow.  Indeed, these reservoirs of snow maintain themselves at the same level, much as a stream, into which many rivulets empty, remains within its usual limits in consequence of the drainage of the average supply.  Of course, very heavy rains or sudden thaws at certain seasons or in particular years may cause an occasional overflow of such a stream; and irregularities of the same kind are observed during certain years or at different periods of the same year in the accumulations of snow, in consequence of which the successive strata may vary in thickness.  But in ordinary times layers from six to eight feet deep are regularly added annually to the accumulation of snow in the higher regions,—­not taking into account, of course, the heavy drifts heaped up in particular localities, but estimating the uniform average increase over wide fields.  This snow is gradually transformed into more or less compact ice,