An Explication of the Sixth Plate.

This Plate is in Reality but one compound Instrument or Apparatus, for trying the Electricity of Glass, and its Luminousness, when put into Motion, and rubb'd upon to heat it. Wherein BC is a Wheel, with its String ABC. DE is a Sphere of Glass, whose Air has been drawn out by the Air-Pump: This is turned round by the former Wheel-string at A. F is a Stopcock, whereby the Air is exhausted, and may be readmitted at Discretion.

In Fig.1. KLM is an Arch with Threads of Cruel or Yarn upon it, as they hang about the Glass DE, (here represented by a smaller Circle within the Arch) before it is turned round or heated by rubbing.

Fig.2. GHI is the same with the former; only the Threads are here represented as they hang at the Beginning of the turning round of the Globe, before it be heated by Friction; being plainly bent one way, by a Wind arising from that Convolution.

Fig.3. NPO is the same; only with the Threads pointing towards the Sphere, or its Center, when the Arch is in an upright Posture, and some of the Threads hang partly downwards, and this upon the Spheres being heated sufficiently.

Fig.4. QSR is the same, with its Threads pointing the same way, though in a downward Posture, when some of the Threads thereby are forc'd to stand erect.

Fig.5. TU is a Circular Arch, in an horizontal Position, when the Threads point towards the same Center, in the same horizontal Plain.

Fig.6. Is another Sphere, communicating with the Air, and to be apply'd to the same Wheel in the Room of DE, where-into is inserted an Axis with a Circle affixed to it; at the Edges of which Circle the Threads are placed. These upon the Friction and Heat of the Glass extend themselves outward, and point from the Center to the Circumference, contrary to the former. In both Cases the Threads, when under the Influence of the Electricity, will be moved by the Finger, even without Contact, nay by the Finger and Breath, even through the Glass it self; so subtle are these Effluvia. The Light is made when the Air is exhausted, and diminishes as you readmit it. It spreads and branches it self inwardly like Lightning, when about half that Air is readmitted. The Colour of that Light is always Purple. It spreads at some Distance, and makes the Edges of a Cravat look a little like the milky Way, by the great Number of Sparkles it emits: Which may also be felt by the Flesh, with a crackling Noise that accompanies them. If you also sufficiently rub and heat a large Tube of Glass, either solid or hollow, it becomes strongly Electrical, even through Glass it self; tho' not so much through Muslin. Other Heat than that by Friction signifies nothing. It will attract and repel Leaf Gold, and the like small and light Bodies, after a strange manner, by turns; when once they have been fully repell'd they cannot be made to touch them, till they have been reflected from some other Body. If they lye between two Pieces of Wood, laid pretty near, the Electricity fails of its Effect. With other Circumstances very surprizing and unaccountable.

FINIS.