A living writer (Mr. John Murray) whose learning and skill in conducting experiments give no little weight to his opinions, has carried these views considerably farther. “The aëronautic spider,” he says, “can propel its thread both horizontally and vertically, and at all relative angles, _in motionless air_ and in an _atmosphere agitated by winds_; nay more, the aërial traveller can even dart its thread, to use a nautical phrase, in the ‘wind’s eye.’ My opinion and observations are based on many hundred experiments.... The entire phenomena are electrical. When a thread is propelled in a vertical plane, it remains perpendicular to the horizontal plane always upright, and when others are projected at angles more or less inclined, their direction is invariably preserved; the threads never intermingle, and when a pencil of threads is propelled, it ever presents the appearance of a divergent brush. These are electrical phenomena, and cannot be explained but on electrical principles.” “In clear, fine weather, the air is invariably positive; and it is precisely in such weather that the aëronautic spider makes its ascent most easily and rapidly, whether it be in summer or winter.” “When the air is weakly positive, the ascent of the spider will be difficult, and its altitude extremely limited, and the threads propelled will be but little elevated above the horizontal plane. When negative electricity prevails, as in cloudy weather, or on the approach of rain, and the index of De Saussure’s hygrometer rapidly advancing towards humidity, the spider is unable to ascend[162].” [162] Loudon’s Mag. of Nat. Hist., vol. i. p. 322. Mr. Murray tells us, that “when a stick of excited sealing-wax is brought near the thread of suspension, it is evidently repelled; consequently, the electricity of the thread is of a negative character,” while “an excited glass tube brought near, seemed to attract the thread, and with it the aëronautic spider[163].” His friend, Mr. Bowman, further describes the aërial spider as “shooting out four or five, often six or eight, extremely fine webs several yards long, which waved in the breeze, diverging from each other like a pencil of rays.” One of them “had two distinct and widely diverging fasciculi of webs,” and “a line uniting them would have been at right angles to the direction of the breeze[164].” [163] Experim. Researches in Nat. Hist., p. 136. [164] Mag. Nat. Hist. vol. i. p. 324. “Such is the chief evidence in support of the electrical theory,” says Mr. Rennie; “but though we have tried these experiments, we have not succeeded in verifying any one of them. The following statements of Mr. Blackwall come nearer our own observations.