1381.] On Production of Transient Electric Currents. 



21 



scopic sections, and teasing and dissection of the brain. The true 

 striate ganglion is mapped off from the olfactory area and deep 

 medulla by the peculiar formation which I have termed from its con- 

 figuration the olfactory lyre. In front of the thalamus opticus the 

 coronal connexions betwixt the striate ganglion, capsule, and cerebral 

 cortex arise, par excellence, from that marginal aspect of the 

 hemisphere at the vertex, which has been stated to be characterised 

 by an extremely rich ganglionic formation — a region entering largely 

 into the composition of Ferrier's motor realm. As the motor ganglia, 

 however, retire outwards before the intervening thai ami, their coronal 

 connexions arise chiefly from the upper and outer aspect of the hemi- 

 sphere, and still further back from the occipital cortex at their own 

 level. Lastly, the median cortex of the upper limbic arc has through- 

 out its course no connexion whatever with the striate ganglion or 

 internal capsule. 



VII. " On the Production of Transient Electric Currents in Iron 

 and Steel Conductors by Twisting them when Magnetised 

 or by Magnetising them when Twisted." By J. A. EwiNG, 

 B.Sc, F.R.S.E., Professor of Mechanical Engineering in the 

 University of Tokio, Japan. Communicated by Professor 

 H. C. Fleeming Jenkin, F.R.S., Professor of Civil Engineer- 

 ing in the University of Edinburgh. Received Septem- 

 ber 7, 1881. 



(Abstract.) 



An iron or steel wire subjected to longitudinal magnetisation by a 

 surrounding solenoid gave when twisted a current along itself, which 

 was observed by means of a ballistic mirror galvanometer in circuit 

 with the wire. When the twist was that of a common screw the 

 transient current flowed along the wire from the nominal to the 

 nominal S. end. An opposite twist gave an oppositely directed 

 current. 



Reversal of the longitudinal magnetisation of the wire, when it was 

 held twisted, gave a strong transient current, but mere interruption 

 or reapplication of the magnetising current gave effects so relatively 

 feeble as not to admit of measurement by the same appliances. When 

 there was no torsion on the wire, reversal of the magnetising force 

 gave no current. The first application of the magnetising force after 

 the wire was twisted gave a current. 



A permanently magnetised wire gave when twisted a transient 

 current of the same sign as that described above (from N. to S. if the 

 twist was that of a common screw). 



