On August 21, 1962, a continuously recording inverted field mill, installed on an open semidesert area near the NMIMT campus, recorded the passage of a fairly large dust devil at a time when I was present to make visual observations. Its closest approach to the field mill was about 450 m, established by reference to power line poles and roads. The bulk of the visible dust cloud was contained roughly in a vertical cylinder estimated to have a diameter of 20 m and a height of 120 m. Experience acquired in observation of many other dust devils suggests that the vortex must have extended far above the height of 120 m; in this case the part above this height was not visible against the mountain background and the dust density in it was probably relatively low. The bulk of the dust seen was probably outside the vortex proper.The transcribed potential gradient record for this event is shown as the solid curve in Figure 1, where it is seen that the gradient was depressed for 10 rain; the lowest value was about 111 v m -z below the level of 49 v m -• prevailing before and after the event. The average general wind speed was about 4 m sec -•, measured by an anemometer near the field mill. The dotted curve of Figure I is a theoretical one representing the effect of a straight line passage, at 450 m, of a simple vertical dipole with a ground speed of 4.0 m sec -z. The electric moment of this hypothetical dipole is 1.13 coul m. (No implication regarding the actual structure of the dust devil is intended at this point;with a structure having a height of the order of 100 m, at distances of 450 m and greater, it is only the nei electric moment of the structure and its image that is of concern.) The agreement between the two curves preceding the minimum is excellent; the moderate divergence beginning about 2 rain after the minimum suggests a diminishing intensity of the dust devil, or an increasing ground speed, though the maxi-mum amount of the divergence is within the range of the 'noise' present.The simplest model having the apparent electric moment would be a uniform distribution of negative space charge density in the approximately cylindrical dust cloud (taken together with its image, of course). If the cloud dimensions are those estimated, this model is required to contain a space charge density of 1.6 X 106 el cm -3 (el --elementary charge).If it is assumed that the diameter was underestimated and that it actually was as large as 30 m, the corresponding space charge density is about 0.7 X 106 el cm -3. If the lower part of the visible dust column was occupied by positive space charge, a possibility discussed below, the negative charge density in the remaining part of the column would have to have a value even larger. Space charge densities of the order of 106 el cm -3 may seem at first glance to be improbably high, in view of the densities usually encountered in the atmosphere. It is quite possible, however, that the dust particle density in o -20

A new range of muzzle velocities has been achieved by propelling a projectile in a gun barrel by a column of hydrogen or helium instead of the conventional powder gas. The first gun built, the design of which probably was far from optimum, yielded muzzle velocities in excess of 12 000 ft/sec with spherical and cylindrical steel projectiles.

Passive antennas were used to make precise measurements of potential at heights of 0.25, 0.50, 1.0, and 3.0 m. These measurements, combined with space charge measurements at ground level and at 1.0 m, permit construction of reasonably definite potential gradient and space‐charge profiles up to the 3.0‐m height. Profiles are exhibited for three types of fair weather situations: (1) normal daytime, (2) nighttime with wind speed greater than 1 m sec−1, and (3) nighttime with wind speed below 0.5 m sec−1. Profiles for the first two situations are of the type to be expected in the presence of electrode effect and eddy diffusion. In the nighttime low‐wind situation, on the average, a stratum of dense positive space charge approximately 0.25 m deep lies next to the ground; negative space charge of moderate density is present above this for the rest of the 3 m. This space charge profile would appear to be a manifestation of the presence of a shallow stratum of relatively intense ionization close to the ground during the nighttime periods of low wind, and thus of the accumulation of Rn222 and Rn220; radioactive elements in the soil near the surface also would contribute.

Measurements of electric moment are reported for seventeen New Mexico dust devils. Estimates of charge and charge density were made for eight of these; charge densities appear generally to be of the order of 106 elementary charges cm−3. Ground speeds ranged from 5–11 m sec−1.

Specimens of sedimentary materials from formations distributed over the sequence from Recent to Ordovician have been processed for recovery of magnetic particles. Magnetic particles were found in all specimens, and among them were black spherules in numbers ranging from 28 to 240 per gram of sediment. These are apparently identical to and have the same size distribution as the black, magnetic spherules currently being collected from the atmosphere and to the magnetic spherules of supposed meteoritic origin that for many years have been reported in deep sea sediments. Two specimens of deep sea sediment were among those studied. They were found to contain larger spherules in numbers of the same order as those reported by Laevastu and Mellis, but spherules smaller than 40 μ in diameter were much more abundant. A large and, thus far, unresolved discrepancy appears to exist between the annual infall of spherules calculated for the deep sea sediments and that calculated for the San Agustin playa deposits and for the present atmospheric deposit.