248 On the Question — Is there Identity between the 



If we now suppose that some loose small pieces of ice have got 



entangled in the plants in the bed of a stream, and around these as 

 a nucleus water continued to freeze, what should be the texture of 

 such ice? 



I have observed in rapid parts of small streams, where stout twigs 

 of decayed hawthorn touch the current, clear nodules of solid ice are 

 often found ; while, when an elastic willow branch touches the water, 

 it collects a mass of white ice, through its continual plunging and 

 rising. When a thin sided vessel of water is suspended in a frosty 

 atmosphere, ice first forms on the surface, and then stretches in shoots 

 of clear hard ice down the sides, and if the vessel is large the ice 

 forms a model of its interior surface. When the upper surface of 

 the same vessel is thickly covered over with a good non-conductor of 

 heat, then hard solid ice is formed under water on the thin exposed 

 part ; again, with the same arrangements, if the bottom be made 

 porous a considerable mass of bottom ice is then obtained, which, in 

 every case I have tried, was solid. If the vessel be immersed in a 

 freezing mixture of salt and snow, hard white ice is produced with 

 unboiled water, and with water well freed from air, hard opalescent 

 ice due to a fine grained crystal, with the portions, frozen after the 

 severity of the cold had relaxed, very transparent. All these facts 

 tend to prove that ice formed in the bed of a stream where no air 

 reaches, and where the rate of freezing can never be rapid, should 

 be solid like the nodules on unyielding nuclei at rapids on the sur- 

 face, or like the ice formed in the bottom of a porous vessel. 



In examining this question, the most difficult part to determine, 

 is the freezing together of scales after they have been entangled in 

 the bed of the stream . Had the w^eather, at the time I found frozen 

 clusters of scales on the plants, at all favoured the supposition that 

 they had frozen together under water, I would have returned filled 

 with doubts and hesitations as to the truth of the entangling hypo- 

 thesis, but the previous weather rendered this impossible. The ex- 

 planation I have given of the submergence of these clusters will, I 

 believe, be found to hold good for other localities ; when the general 

 explanation of the phenomenon of ground-ice for the climate of 

 Great Britain, will become simply this : — That it is all, either 

 formed on, or thrown in on, the surface^ and made to assume an 

 unnatural position by the mechanical action of the current. 



On this question — Is there identity between the Species of the 

 Secondary and Tertiary Formations, and those belonging to 

 the Existing Generations ? 



We readily learn, by comparing the ancient generations 

 with those that are contemporary with ourselves, that they 

 have nothing in common with regard to their specific type, 



