substances, galena or tellurium, or, as before mentioned, other substances which do not themselves give the characteristic curve may be used if suitable conditions or agencies be caused to act upon them to cause them to give such a characteristic curve, and thus become self-recovering. As shown, one of the contact-pieces 4 5 may be cylindrical in shape and of uniform dimensions and the other taper to a point. The contacts 4 5 are normally held together by a spring 6, arranged between the arms 1 2, and the pressure of which can be regulated with great delicacy by means of a micrometer-screw 7, provided for the purpose. The pivoted arms 1 2 and their spring 6 are fitted in a tube 10, of ivory or other insulating material, this being in turn inserted in the tubular extension 11 of a hemispherical or other suitably-shaped metal case 12, which may conveniently constitute a reflector.
The tube 10 carries a pin 10a, engaging in a bayonet-slot 11a of the extension 11 to enable the tube 10 to be readily inserted and secured in said extension, or any other suitable means may be provided with the same object, as will be readily understood. The part 12 of the instrument may be inclosed, as shown, in a wooden or other shell 12a 12b, of spherical or other form, and which may for convenience be made in sections adapted to be connected together by pins fitting into suitable holes, as shown. A chamber 12c is thus constituted. A hole is provided in the section 12b of this chamber, in which a lens may be placed, as hereinafer described.
By means of the insulating-cheeks 8 9, tube 10, and insulating bearing-surface 14 of the spring 6 the conducting-arms 1 2 are insulated from the case and from each other except at the point of contact of the sensitive contacts 4 5.
A female thread is provided at a suitable point of the extension 11 to receive the micrometer-screw 7, this screw passing down through or escaping the end of the insulating-tube 10 and bearing upon the upper arm 1. The micrometer-screw should be provided with an insulating-head. By turning the screw 7 the pressure of the spring 6 may thus be adjusted with great nicety in order to adjust the force of contact between 4 and 5.
Wires 15 16, preferably insulated wires, lead, respectively, from the arms 1 2 and pass out through a plug 17, of cork or other insulating material, fitted in the end of the extension 11. By means of these wires the arms 1 2 and contacts 4 5 may be connected up in the circuit of an electric battery or other source of electricity 18, in which circuit a sensitive galvanometer 19—for example, a dead-beat d'Arsonval galvanometer—is interposed as an indicator. Instead of a galvanometer other suitable electric indicating or recording apparatus may be used.
The contacts 4 5 may project to any desired extent into the chamber 12c, according to the focus of the lens fitted in the opening therein. The tube 10 with the arms 1 2 may be movable in the extension 11 for the purpose of focusing the contacts 4 5 with respect to the lens employed.
By placing an ordinary glass lens 13 in the opening in the wall of the case-section 12b opposite the sensitive contacts 4 5 of the instrument and by throwing light upon this lens an immediate response is observed in the galvanometer, the needle of which is deflected in accordance with the spectral properties of the light thrown upon the sensitive contacts or artificial retina. With a glass lens the instrument will detect and record lights not only some way beyond the violet, but also in regions far below the infra-red in the invisible regions of electric radiation. We may thus style the apparatus a "tejometer" (Sanscrit tej = radiation) or universal radiometer.
Instead of using an ordinary glass lens, as above described, we may use a water-lens, and in this case the range of what we may term the "spectral vision" of the instrument may be reduced to a level which more nearly corresponds to that of the human eye, the water-lens absorbing the naturally invisible radiations before they reach the sensitive substances of the instrument corresponding to the retina viva.
By removing the metallic and wooden casings and lens the instrument may be used as a detector or so-called "coherer" for wireless or other telegraphy.
The apparatus hereinbefore described is self-recovering when the sensitive substances used therein have a characteristic curve of the kind before described—that is to say, that the distortion produced in the sensitive contacts by a wave or radiation caused to impinge thereon is automatically removed upon the cessation of the wave or radiation and leaves the sensitive substance in statu quo ante, or, as above mentioned, the same effect can be obtained by subjecting or exposing the sensitive substances in the apparatus to influences or agencies which will cause them to give the curve in question.
What I claim, and desire to secure by Letters Patent, is—
1. In a coherer or detector of electrical disturbances, Hertzian waves, light-waves or other radiations, a sensitive substance having a characteristice curve (giving the relation between an increasing impressed electromotive force and the resultant current passing through the sensitive substance), which is not straight but is either convex or concave to the axis of electromotive force and in which the return curve with a decreasing electromotive force when taken slowly, approximately coincides with the former curve.
2. In and for a coherer or detector of electrical disturbances, Hertzian waves, light-
