The hypothesis that lightning fires are caused by a special type of lightning discharge has been presented several times in literature over the past 20 years. Working with laboratory sparks, McEachron and Hagenguth [1942] suggested that ignition by natural lightning is usually caused by a discharge having a long‐continuing current phase. This view is widely accepted [Berger, 1947; Malan, 1963; Loeb, 1966], even though field corroboration has been almost nil. To the authors' knowledge, the two discharges and resultant fires documented by Norinder et al. [1958] are the only natural events reported to date wherein both the discharge and its ignition effects were documented.

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Of 16 documented lightning discharges 11 caused forest fires in western Montana forests. All 11 discharges exhibited a long‐continuing current (LCC) phase of at least 40 msec duration. Of the 5 non‐fire discharges, 2 had LCC phases and 3 did not. Results to date strongly support the hypothesis that forest fires are caused by discharges with long‐continuing currents. However, available data suggest that discrete discharges (cloud‐to‐ground discharges without LCC portions) cannot be entirely ruled out as a source of forest fuel ignition.

Acoustic reflectometry has been shown to be an effective technique for detecting defects, such as holes and blockages, in relatively short, single lengths of pipe. This paper discusses briefly the physical basis of the technique and then describes the results of a series of experiments that were designed to evaluate the suitability of using this approach for monitoring the health of natural gas pipelines. Such pipelines will typically be many kilometres long, have diameters of up to 1 m and may form part of a complex network of pipelines. Previous studies have demonstrated that acoustic reflectometry techniques can be used to detect pipeline defects in relatively small bore pipelines with lengths of several hundred meters. The results reported in this paper indicate that even when using fairly crude equipment, the technique can be successfully applied to detect defects in single pipelines and pipeline networks with large diameters and lengths exceeding 5 km. Although the results presented in this paper are not conclusive, they do provide the necessary justification for a second phase of experiments to be conducted to extend the scope of the technique further.