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ALTHOUGH the treatment of cancer of the uterine cervix is now almost entirely radiological, the best method of irradiation is still unsettled. The merit of any technique is customarily assessed on its five-year salvage, but this is unsatisfactory in so far as judgment is based on an incomplete picture of the results of therapy. The wide employment of radium in advanced cancers demands an evaluation of its effects from the standpoint of palliation as well as of cure, and this is not possible without some knowledge of the dangers associated with its use: I t is the purpose of this investigation to examine the complications of therapy in 650 consecutive cases of cervical cancer irradiated in the Gynaecological Department of the Cardiff Royal Infirmary. In the earlier years the supply of radium was contained in IZ needles with a screenage of 0.5 mm. of platinum, which were embedded in and about the tumour as previously described by Strachan.' From 80 to 120 mg. of radium element were so applied, usually for a period of 24 hours. In 1930 interstitial irradiation was abandoned in favour of a fractional intracavitary method based on the technique introduced by Heyman of Stockholm, and this is the method still employed. A tube of 50 mg. of radium is placed in the uterine cavity, when this is easily effected, and one or more silver boxes containing a total of 50 to 80 mg. are apposed to the vaginal aspect of the growth. The applicators are enveloped in thin rubber and screenage is the equivalent of 1.5 mm. of platinum.Two exposures, each usually of 30 hours, are given, separated by an interval of one week. In both methods the vagina is firmly packed with gauze, and an indwelling catheter is used during irradiation. The patient subsequently receives a daily vaginal

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A ray‐tracing technique has been used to determine the properties of one‐hop propagation. It was found that long‐distance one‐hop propagation may occur via the F1 as well as via the F2 layer, that gaps may occur in the range of frequencies propagated, and that only low‐angle propagation is possible at 0° elevation angle. It was found that one‐hop propagation may occur to distances in excess of 7500 km in temperate regions and 10,000 km in equatorial regions. For a given ionosphere, the limiting distances over which the propagation may be observed is determined by the signal‐to‐noise ratio. Transequatorial long‐distance one‐hop propagation can be explained on the basis of normal one‐hop propagation. The results obtained from the ray tracing were compared with sweep frequency soundings taken on the 5600‐km circuit between Ottawa, Canada, and The Hague, Netherlands. On this circuit, during 1960, one‐hop propagation was observed 35 per cent of the time that two‐hop propagation was present. One‐hop propagation regularly occurred during the summer daytime.

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