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The measurement of the erosion at the electrodes of an arc rotated between water-cooled nonrefractory coaxial electrodes in an axial magnetic field has been made in air at atmospheric pressure. Values of erosion rate an order-of-magnitude less than those previously reported have been obtained. The effect of variation in axial magnetic flux density, arc velocity, rotational frequency, cooling-water flow-rate, and electrode wall thickness have been investigated. A steady-state model, taking into account the nonuniform thermal distribution in the electrode below the arc root, has been obtained in terms of the electrode dimensions normalized with respect to the diameter of the arc root. The minimum conditions for the surface of a cold-cathode electrode to be maintained below the melting point of the electrode material are deduced.

Although the brownish area at the corneal periphery in the region of Descemet's membrane was first described by Kayser (I902), and Fleischer (I9I2) recognized it as a part of Wilson's disease (hepato-lenticular degeneration), there have been no previous reports in the ophthalmic literature of the United Kingdom of a pathological study of the lesion which is now recognized as a pathognomonic finding in this disease. Case Report CLINICAL HISTORYThe patient, a young man who was the only child of unrelated parents was involved, at the age of I 9, in a road accident in which he was knocked unconscious. On recovering consciousness he was found to be suffering from a loss of balance, together with deafness in the left ear; tremor of the head and hands developed later and this spread to involve the lower limbs. It was, however, several years before a diagnosis of Wilson's disease was made and treatment with British anti-Lewisite begun. There was an initial improvement, but this was not maintained, and when the dose was increased visual disturbance and muscular cramps developed. A course of penicillamine treatment was commenced and this resulted in considerable improvement. The treatment was, however, rather sporadic and after a few days the patient had the first of several haematemeses; these were shown to be associated with oesophageal varices, and a splenectomy and spleno-renal shunt was performed. His condition subsequently deteriorated dramatically and in spite of intensive treatment with penicillamine he lapsed into a comatose state in which he remained for a year before he finally died at the age of 34, some I5 years after the initial onset of symptoms. OPHTHALMIC EXAMINATIONThe cornea of each eye showed a broad complete Kayser-Fleischer ring. BIOCHEMICAL STUDIESThese showed a very low caeruloplasmin and serum copper typical of Wilson's disease. PATHOLOGICAL EXAMINATION (a) GeneralThe most striking features of the post mortem examination were seen in the brain and liver. The former showed conspicuous cortical atrophy, mainly over the frontal and parietal areas, wasting of the putamen, and a small thalamus and mid-brain. The liver showed a nodular coarse cirrhosis. Other findings included portal vein thrombosis and areas of bronchopneumonia.This communication is dedicated to Prof. Dr. Josef Bock, Chief of the Second Eye Clinic of the University of Vienna, on the cccasion of his 70th birthday.

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