This operation was started at 5: 00 p.m. and lasted for 29 minutes. There was a slight lapse condition, a moderate fog, and 100 per cent relative humidity. A network of sampling stations had been set up on shore. These were located at the homes of Government employees, in Government Offices, buildings and reservations within the trial area. A rough attempt was made to characterize the vertical profile of the cloud by taking samples from outside the windows on the first, ninth, and fifteenth floors of a Government office building.

All samplers were operated for a period of two hours except one, which was operated for four hours. In this instance, there was a dosage of 562 during the first two hours and a total dosage of 1980 for the four hour period, a four-fold increase. This suggests that the sampling period, particularly at the more distant locations, should have been increased.

As can be seen from Figure 2, an extensive area was covered by this aerosol. The maximum distance sampled was 23 miles from the source. As can be seen from these dosage isopleths, approximately 100 square miles was covered within the area sampled. It is quite likely that an even greater area was covered, particularly downwind.

The dosages in the three levels of the vertical profile were: ** f This was not, of course, enough sampling to give a satisfactory description of the vertical diffusion of the aerosol.