Royal Society. 193 



of voltaic electricity conducted, or the force of the current, was a 

 function of a greater number of variables than had been previously 

 supposed. As the theory which he proposed for estimating the con- 

 ducting powers of substances has been controverted by M.Lenz*,he 

 has been induced to reconsider the subject, and finds reason to be 

 satisfied with the correctness of his former views. He farther finds 

 that with feeble magnetic needles the deflecting forces are not pro- 

 portional to the force of the current, but approach nearer and nearer 

 to that proportion by increasing the magnetic power of the needles ; 

 a result which the author thinks is strictly deducible from the uni- 

 versal law of nature, that the attraction mutually exerted by two 

 bodies is measured by the sum of their masses. He shows that the 

 formula of Ohm, expressive of the conducting powers of wires, and 

 of the resistances which they offer to currents of voltaic electricity, 

 is an approximation to the truth only in the case of feeble currents, 

 and that with the same metal, the conducting powers are not as the 

 lengths of the wires. 



The author next inquires into the relation between the heat de- 

 veloped, which he finds to be, in the same wire, as the square of the 

 intensity of the current ; and in wires of the same diameter, and 

 conducting equal quantities of electricity, it is inversely as the con- 

 ducting power, or directly as the resistance which they oppose to 

 the current. The facts he has adduced in this paper seem to be at 

 variance with the generally received theory of caloric, and to be in 

 perfect accordance with the undulatory theory. 



He concludes by describing an experiment confirming the views 

 he has elsewhere advanced with regard to the difference between the 

 physical, the physiological, and the chemical effects resulting from 

 the employment of coils formed of wires of different lengths, being 

 dependent on the time required by the conductor for returning to 

 its natural state. 



" On the Ipoh or Upas poison used by the Jacoons and other 

 aboriginal tribes of the Malayan Peninsula." By Lieut. T. S. New- 

 bold, Aide-de-Camp to Brigadier- General Wilson, C.B. Communi- 

 cated by P. M. Roget, M.D., Sec. R.S. 



The author gives an account of the process by which the Jacoons, 

 an aboriginal tribe inhabiting the mountains and forests of the Ma- 

 layan Peninsula, prepare the poison applied to the points of the 

 slender arrows which are propelled from the Simpitan or blow-pipe. 

 Three preparations are employed for this purpose, distinguished by 

 the names of Krohi, Tennik or Kennik, and Mallaye ; the last of 

 these is more powerful than the other two, and is obtained from the 

 roots of the Tuba, the Perachi, the Kopah, and the Chey, and from that 

 of the shrub Mallaye, whence it derives its name. The Krohi poison 

 is prepared from the root and bark of the Spoh tree, and the roots 

 of the Tuba and Kopah, with the addition of red arsenic and the 

 juice of limes ; and the Tennik from the same ingredients, omitting 

 the Kopah root. A i'ew experiments are related, made by the au- 

 thor with a view to ascertain the effects of the poisoned arrows on 

 * See Scientific Memoirs, vol.i. p. 311. 



Third Series. Vol. 11. No. 66. Aug. 1837. 2 C 



