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T HE differential scattering cross sections for 20.4±1.0-Mev alpha-particles by helium were determined at center-ofmass scattering angles of 60° and 90°. The experimental results are shown in Table I.The scattered particles were detected by a proportional counter. The amplified pulses from the counter went to a pulse-height discriminator circuit which rejected pulses of amplitude appreciably smaller than those desired. The unscattered particles were collected in a faraday cage which was connected to a one-^if condenser. The voltage across the condenser was measured by a null method using a Compton electrometer as the null device.There was an appreciable background counting rate resulting from the neutron flux accompanying the operation of the cyclotron. This background was reduced somewhat by shielding the counter with borax and paraffin. The background counting rate was determined before and after each set of scattering runs. Based on the internal consistency of the background data and the number of counts taken, a precision of db 10 percent was assigned to the background correction.The scattering chamber was filled to a pressure of about 2.2 cm of Hg with helium of 99.5 percent purity furnished in standard cylinders by the Ohio Chemical Company. The pressure was determined by a U-tube manometer filled with Apiezon oil B. Impurity scattering is not believed to be important in this work because the alpha-alpha scattering cross section is at least as great as the alpha-air scattering cross section for the angles studied, hence the possible 0.5 percent impurity in the scattering gas could contribute a maximum error of 0.5 percent. Furthermore, the pulses produced by impurity-scattered particles were smaller than the genuine pulses, and experimental tests showed that impurity-caused pulses were counted with poor efficiency. Outgassing of the metal surfaces of the scattering chamber or leaks in the system would have caused the pressure of the scattering gas to increase during a period of data taking. No increases in pressure greater than one percent were noted.No direct data on the cyclotron alpha-particle beam energy are available, so it has been estimated from measurements of the proton and deuteron beam energies. The probable errors quoted for the scattering cross section in Table I include the statistical probable error, the probable error in the background counts, and a collection of minor errors that are discussed in a paper on protonalpha scattering 1 in which the same apparatus was used. A more TABLE I. Results of the alpha-alpha scattering work for incident alphaparticles of 20.4 ±1.0 Mev. d is the scattering angle in the center-of-mass system, n is the number of counts observed, R is the ratio of the number of genuine counts to the number of background counts, and a is the differential scattering cross section in the center-of-mass system expressed in barns/sterad. 6 n R a 60° 900 19 0.086 (±5.5 percent) 90° 900 26 0.14 (±5.5 percent)detailed account of the apparatus and the procedure used in taking data ar...

butable to ether or chloroform, in order to satisfy practitioners I that" a meddlesome midwifery is still a bad midwifery." i What should we think of the man who enumerated the I poisonous phenomena manifested by an overdose of opium for I the purpose of altogether abrogating its use ? Southampton, April 14,1848. REPORT OF AN EXTRAORDINARY DOUBLE-BIRTH. BY W. F. ASKHAM, Esq., Surgeon, Eckington, Derbyshire. I WAS called upon, on the 3rd of February last, to attend a healthy young woman, then in labour of her fourth child, and according to her own statement, at the full period of utero-gestation. As there had been haemorrhage to some extent previous to my arrival, I at once made an examina

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nutshell dimensions, and that after spelling through musty records, and translating half-obliterated charters, it simply resolves itself into this important fact-that the charter of King's College and University, specially expresses the authority of the " Senatus Academicus" to confer various degrees, while the charter of Marischal College and University only does so generally, as appertaining to a University.-I am, &c.