[122] The only chemical difference between _Cleavelandite_ and _Felspar_ is, that about 12 per cent. of Potass in the latter is replaced by an equal quantity of Soda in the former. The earthy ingredients in both minerals are the same, and exist in similar proportions. The primary form of each is a doubly oblique prism, but the two prisms differ so essentially from each other in the measurement of their angles, that the substances are easily distinguished from each other by the Goniometer. EXCURSION VI. TO KYNANCE COVE, AND THE LIZARD POINT. An excursion to the peninsula of the Lizard offers to the scientific traveller many objects of great geological interest; he will be enabled to examine a very rare and important series of Rock Formations, while their various gradations and transitions into each other will afford ample materials for speculation. In the course of this excursion it will be our duty to point out some of the more prominent features as they may occur in our progress; but in performing this duty we wish to be considered as merely presenting the geologist with a rough and imperfect outline, which may give a useful direction to his researches, and enable him to acquire, through the medium of his own observation, more ample and perfect information.[123] To the country south of a line drawn from the mouth of the Helford river, on the east, to the Loe-Bar on the west, has the appellation of the "_Lizard District_" been exclusively applied by Mr. Majendie; and the division appears to have been conventionally received by all the geologists who have traced his steps. The fundamental rock of this peninsula appears to be _Clay-slate_, associated with _Greywacké_, upon which are successively deposited _Greenstone_, _Diallage rock_, and _Serpentine_. At Marazion several alternate beds of _Slate_ and _Greenstone_ may be observed; the latter of which contains _Asbestus-Actynolite_, and is universally traversed by veins of _Axinite_,[124] which occurs both in an amorphous and crystalline form. In the vicinity of a projecting ledge of rocks, known by the name of _Cuddan Point_, stands a mansion called _Acton Castle_, which was erected as a marine residence by the late John Stackhouse, Esq. and is at present occupied by Capt. Praed. Its situation is wild and unsheltered, but it commands a prospect of very extraordinary grandeur and beauty.