Memoirs of the National Academy of Sciences . end this contact for closing a circuit; a circuit maybe readily broken, but in orderto close a circuit a mercury contact is nearly always used, which involves various inconveniencesand sources of error. By means of this wheel contact a current can be closed at a given instantand remains closed, or the circuit could be closed for any given fraction of a hundredth of asecond, which might be useful for many experiments. The rubbing keeps the contacts clean. In the Hipp chronoscope tho latent time of magnetization is mncU larger than necessary. The ele
Memoirs of the National Academy of Sciences . end this contact for closing a circuit; a circuit maybe readily broken, but in orderto close a circuit a mercury contact is nearly always used, which involves various inconveniencesand sources of error. By means of this wheel contact a current can be closed at a given instantand remains closed, or the circuit could be closed for any given fraction of a hundredth of asecond, which might be useful for many experiments. The rubbing keeps the contacts clean. In the Hipp chronoscope tho latent time of magnetization is mncU larger than necessary. The electro-magnet has a very high resistance and si-lf-induction, au<l the levers carried by the armature are needlessly complicated and heavy. We have, as stated, greatly reduced the latent time by rewinding the magnets with coarser wire. We .are -rure that a chronoscope could be constructed in every way better than that by Hipp, and it is only the expense which has prevented us from making one. 398 MEMOIRS OF THE NATIONAL ACADEMY OF MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 399 The current in these wheels does not pass through the points of the axis (which might causevariation in the resistance), but through a platinum spring, <S, which touches the side of the wheel. The falling screen and contacts described make a cliroiioscopc useful for many psychological,physiological, and perhaps physical purposes. We have used the iustrument chiefly to sinuil-taneously close and break currents, and to give a standardinterval of 100 ff (one-tenth second) for the regulation of thechronoscope. In two other directions, however, experimentshave been begun with the instrument. Electric shocks areproduced separated by (say) 10 a. These shocks are appliedto the nerve at varying distances from the brain, the eailiershock having farther to travel. When the shocks are feltsimultaneously we have measured the time it takes to travelthe distance between tlie two contacts. This method in
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