This stratum is never wrought by the workmen, being arenarious, and too soft for their use. It is about four or five feet thick, and forms a kind of roof to them, as they dig out the stone, of which the slates are formed; for they work these pits in the same manner as they do the coal-pits, leaving pillars at proper distances to keep their roof from falling in. This last bed of slate-stone is about five feet depth, and lower than this they never dig. So that the whole depth of the pit amounts to about 24 or 25 feet. It was by working out the slate-stone, that this bone was discovered sticking to the roof of the pit, where the men were pursuing their work; and with a great deal of caution, and no less pains, they got it down intire, but attached to a large piece of stone; and in this state it now remains in my possession. There is no water in the works, but such as descends from the surface thro’ perpendicular fissures; and the whole is spent in forming the stalactites and stalagmites, of which there is great variety, and whose dimensions are constantly increasing. One of the workmen has been so curious, as to mark the time of the growth of some of them for several years past. I am, with the greatest esteem, Dear Sir, Your ever obedient, and most humble Servant, Joshua Platt. Oxon, Jan. 20. 1758. LXIX. _A Discourse on the Usefulness of Inoculation of the horned Cattle to prevent the contagious Distemper among them. In a Letter to the Right Hon._ George _Earl of_ Macclesfield, _P. R. S. from_ Daniel Peter Layard, _M. D. F.R.S._ [Read Feb. 2, 1758.] My Lord, THE honour you have done me, in condescending to peruse my Essay on the contagious Distemper among the horned Cattle, claims my most respectful thanks; and I am no less obliged to your Lordship for the just remark you made, “That before inoculation could be practised on the horned Cattle, it is necessary to bring proofs, that this disease is not susceptible more than once; and also assurances, that a recovery from the distemper by inoculation guards the beast from a second infection.” An intire conviction of the analogy between this disease and the small-pox would not permit me to omit mentioning the great advantages, which must arise from inoculation; and therefore, my Lord, I recommend its use: nor do I find any reason to alter my opinion, after having carefully read over what has been published, and made the strictest inquiry I was able in several parts of Great Britain. I shall, in the concisest manner possible, submit the following particulars to your Lordship’s consideration, and the learned Society, over which you so deservedly preside.