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A number of manufacturing processes are adversely affected by the presence of trace amounts of water vapour in purge and process gases. It is important for the operators of such processes to monitor the levels of water vapour in these gases continuously. There are many analytical methods for determination of trace water vapour which all require regular, traceable calibration. In this paper, a new standard facility for generating an adjustable level of trace water vapour is described. It uses continuous accurate measurements of the mass loss from a permeation device coupled with a dilution system based on an array of critical flow orifices. Details of the verification of the facility are presented along with results of comparisons with the National Physical Laboratory thermally-based dew/frost point humidity standards facility.

The distribution of rabbit warrens on six different classes of country in the semiarid pastoral area of New South Wales was assessed by aerial survey from an altitute of 300 m, at a ground speed of 110 km/h, on a complete cover basis. Ground assessment of warren distribution showed that the proportion of warrens found by aerial survey varied between a 94% underestimate and a 13 % overestimate. This variation shows a strong correlation with mean warren size.

The effectiveness of warren ripping as a method for controlling rabbits in a semi-arid environment was tested on a 3000 ha site at Kinchega National Park in western New South Wales. Estimates of rabbit numbers made during the study showed that the immediate effect of warren ripping was to reduce the rabbit population by about 65%. The longer term effect was to stabilise numbers at a relatively low level. The only warrens active 14 months after being ripped were those which gained new burrow entrances within two months of being destroyed. Re-opening rate of warrens was greatest for large limestone warrens where 90% of ripped warrens were again active after two months. Less than 30% of all sandy warrens became active again. Within each re-opened warren, the number of active entrances increased slowly but 14 months after being destroyed they had still not reached their original size.

Two methods for obtaining an index of fat reserves in the wild rabbit were tested on animals collected over a period of 14 months from six locations in semiarid western New South Wales. Marrow fat appeared to have little value except when populations approach starvation, but because few of the study populations approached this point it was not fully evaluated. Abdominal fat index, an estimator based on the weight of the fat depot which lies on the right dorsal side of the abdominal cavity extending from the diaphragm to the pelvic girdle, was found to be more useful for indicating population fat reserves than the marrow fat index. Mean values for each location could be calculated to provide a measure of relative environmental favourability. The index also reflected a population's rate of increase.