The shape and disposition of the platinum thermometer may be modified so as to adapt it to almost any position or method of observation.

Further, the arrangement can readily be made a differential one. Thus, two pieces of platinum, cut from the same specimen of wire, may be inserted-one into each gap, hj and h'j'. Both having nearly the same resistance, the bridge will balance, when they are at the same temperature, at nearly the middle part of the scale. Both thermometers having the same coefficient of temperature, the effect on the galvanometer would at once indicate any difference of temperature to which they might be subjected. Thus, if one of the thermometers were placed in the mouth and the other in the armpit, we should have a ready means of comparing the temperature of the inside and outside of the human body. Similarly the temperature of any two parts of the body might be compared.

The surface temperature is known to vary considerably in certain diseased conditions, and it is of importance to determine these variations from time to time. I have found that a convenient method of arranging the platinum resistance for surface observations is to make two little flat spirals, lay them each between two cover-glasses, and dip the whole into a solution of shellac in spirit. When dry they may be attached to the surfaces to be observed by means of sticking-plaster, and then connected to the bridge.

Again, the temperature change, as the result of muscular action, may be studied by hanging a frog's muscle in the middle of a thin glass tube of sufficient diameter to allow it to hang and contract within it, but without touching the sides of the tube. Round the outside of the tube is coiled a platinum thermometer, and the whole is guarded from outside influence by another tube of glass, paper, or vulcanite. In such an arrangement two or three twitches of the muscle will deflect the spot over several divisions.

Such examples will indicate how easy it is to adapt this arrangement for a variety of purposes in physiological and clinical thermometry.

On an Astatic Galvanometer with Interchangeable Coils. By R. MILNE MURRAY, M.A., M.B., F.R.C.P.E.*

The special features of the galvanometer is the way in which the coils are fixed and connected together, so that their removal and replacement by others is a very simple and safe procedure.

The coils are wound in boxes in the ordinary way.

To the faces of these boxes are attached two brass lugs, in each of which is a vertical slot aa (Plate V.)

The ends of the wire come through the front of the box, and are joined to two copper straps which project from the lower margin of the box bb. These are likewise slotted.

The coils are supported by the lugs aa, which are clamped to the ends of short horizontal arms carried on pillars supported on the vulcanite base of the instrument. When they are dropped into position, the projecting straps bb also fall in between the jaws of a pair of small horizontal clamps also fixed to the base of the instrument. These clamps are connected to the terminals of the galvanometer, so that the coils are properly connected to their respective terminals by the mere act of putting them in position. It will then be seen that, in order to remove one coil and insert auother, it is only necessary to slacken the clamping screws at aa and bb, lift the coil vertically to clear the slots, and then remove it; the other coil can then be as easily dropped into its place, and all connections secured by simply tightening the clamps.

The inconvenience and risk of having to fasten and unfasten loose terminal wires is thus always avoided and good contact at the junctions secured.

* Read before the Society, 27th February 1893.