In explanation of the origin of the invention, Mr. Miller stated that he was a farmer's son, and that, in his youth, he used to be employed at times to assist in catching horses at grass, by means of surrounding them with a rope, borne by a person at each end of it. He remarked that, in this service, although no restraint was laid upon the horses when the rope rested on their chests, yet, whenever it could be got upon their throats, they instantly stood still and allowed themselves to be taken. The idea which this recollection suggested, of the probable effect of pressure on the throat in stopping a runaway horse, led Mr. Miller to the contrivance of his safety-reins. In his first experiment, the band which connects the reins under the neck was attached to the headstall by hooks and straps; but it has been considered an improvement to allow it to move freely upon the reins, on which it settles in contact with the throat, in a proper position for use when required. Our communications with Mr. Miller impressed us favorably in regard to his contrivance; but, wishing to see it in practice we availed ourselves of an offer by him to afford us an opportunity of judging of it in operation. We, accordingly, on a day appointed, accompanied him in a carriage drawn by one horse, for the purpose of trial; and we witnessed as spectators, as well as made ourselves, repeated tests of the reins, with the horse going at a smart canter, both on a level road and on a descent, and we invariably observed that the tightening of the reins caused the horse immediately to stop. No injurious effect seemed to be produced on the horse by the interruption of his respiration. He always appeared to breathe freely, and to be ready to resume his work, as soon as the tension of the reins was relaxed. Upon the whole, therefore, we consider Mr. Miller's invention to be a neat and simple, as well as, to appearance, an effective contrivance for the accomplishment of its important object, in the prevention of the disastrous accidents which not unfrequently occur from horses running away; and we think it reflects much credit on the ingenuity of its inventor. GARDENERS' CHRONICLE.--_Rhododendron._--There is a variety of the Rhododendron ponticum growing here, which appears to be different from any of the others. It comes into flower about the same time as the others, but instead of unfolding its blossoms at the same rate as its neighbors, it only opens a few at a time, and continues long in flower. It did not cease flowering this season the whole month of August; consequently was nearly a month longer in bloom than the others. It has a southern exposure, and is sheltered from the north and east.