Small local dislocations in processed emulsions give rise to spurious scattering whose effect on tracks is indistinguishable from the multiple scattering produced by coulomb interaction. Because of this effect the atomic number of fast primary cosmic ray nuclei will be underestimated in more than 50% of the cases in experiments where multiple scattering of tracks and ionization measurements are employed for charge determination. The spurious scattering was investigated by measuring the track contours of 100 very long tracks due to energetic primary particles; the effect was present in comparable strength in all plates and all types of emulsions which have been investigated. It is too small to affect measurements on medium energy particle tracks (protons with energy below 600 MeV and heavy nuclei with energy below 300 MeV/ nucleon). It dominates, however, other sources or error and noise for tracks of energetic particles although it does not preclude occasional observations of very low scattering values. New methods for measuring various forms of noise have also been developed in the course of this work and the noise level for scattering measurements has been reduced below previously accepted values.

Spurious scattering is presumably largely responsible for the discrepancies which appear when one compares the primary charge and energy spectra derived from experiments involving scattering measurements with the corresponding spectra derived from numerous other experiments which employ different techniques.

If the experiments based on scattering measurements are omitted, the remaining evidence strongly favours a spectrum in which the energy per nucleon is nearly independent of atomic number for all primaries. It also favours a charge distribution which has a pronounced minimum for charges 3≤ Z≤ 5 and, therefore, yields a fairly low upper limit for the amount of interstellar matter traversed by primary cosmic ray nuclei.

The concentrations of tritium have been determined in wet precipitations occurring over the Indian subcontinent during 1961–64, using a sensitive method for counting of tritium activity discussed in Part I* of this paper.

The tritium concentrations varied significantly during the period of observation; highest concentrations were observed during 1963. An analysis of the data reported here, in conjunction with those available for concentrations of H³ and Sr⁹⁰ in rains at higher latitudes, reveals that these nuclides which were originally placed at high altitudes in the polar regions during late 1962, were deposited chiefly at 30°–90° latitudes during 1963 and 1964 respectively in relative proportions of 1 and 0·6. The data show that the largest gradients in their zonal deposition occur at about 35°–40° N latitude and that to a first approximation, their deposition per unit area in 1963 or 1964 was practically uniform, separately in the 30°–90° and 0°–30° latitude regions. This observation suggests the existence of two well-defined cells, which are internally well mixed: the meridional transport to low latitudes occurs as a result of interaction between these cells. The annual deposition rates of Sr⁹⁰ as observed during 1963 and 1964 suggest a mean time of 3 months for exchange of air between the two cells, in good agreement with the values deduced for mid-months of the year on the basis of analysis of bomb produced C¹⁴ data.

The tritium and strontium data for the inland, coastal and island stations are analysed to evaluate the importance of (i) the re-evaporation of tritium from continents, and (ii) the molecular exchange of atmospheric tritium with oceanic water. Process (i) probably plays a significant role over the continents throughout the year; its effect, however, is experimentally visible only during June to September. The estimated concentration of H³ in evaporated water suggests that the precipitated water mixes very slowly with that in the soil; limits on the equivalent amount of exchangeable soil water are given.

It is shown that the relative wet deposition of H³ and Sr⁹⁰ atisland andcoastal stations is similar to their estimated concentration ratio in upper level tropospheric air. Furthermore, the relative concentrations of H³ and Sr⁹⁰ at continental and occanic stations differ only to the extent expected due to reinjection of H³ over continents. Thus, if one takes into account the recycling of H³ at continental stations (which results in about a 50% higher apparent deposition on an annual basis), one is led to the conclusion that process (ii) is rather unimportant; an upper limit of 30% on the fraction of tritium removed over oceans by molecular exchange is deduced.

The mean annual concentration of Sr⁹⁰ in wet precipitation is lower at oceanic stations compared to that at continental stations. This could be due to meteorological effects peculiar to oceanic areas,e.g., higher rainfall and quick recycling of evaporated water. Otherwise, one must postulate a significant removal of Sr⁹⁰ (and H³) by ocean spray and jet action.

Depth variations of environmental tritium and of soil moisture in the unsaturated zone of the semi-arid alluvial tracts of northern Gujarat (India) are measured and utilised to evaluate vertical groundwater recharge. Results obtained from the two different experiments carried out at an interval of two years are found to be in fair agreement. An average of recharge amounting to about 5 per cent is indicated.

The observed depth variation of tritium gives support to the view that the movement of soil moisture in this region is layered.

The downward movement of water in the soil due to 1971 monsoon precipitation and supplemental surface irrigation has been traced at about forty-five sites in Western Uttar Pradesh, using a thin layer of moisture tagged with tritiated water. The tritiated layer was found to move down to different depths at different sites. The movement, averaged over the forty sites is found to be 96 cm, indicating that the average recharge for the year 1971 (a year of normal monsoon) was 21.5 cm of water.

The radon concentrations of air samples collected during the South West monsoon period at altitudes up to 4 km over the Arabian Sea at two locations,i.e., 0–50 km and 300–400 km west of Bombay, are reported. Radon was extracted from air, using a simple single stage apparatus. The concentration of radon in the monsoon air mass was found to range around 80–100 dpm/m³ STP, indicative of its recent continental origin. The results suggest that the coastal monsoon air mass, up to 400 km west of Bombay coast, is generally homogeneous and vertically well mixed.

During the post-monsoon condition, a strong gradient in the radon concentration in the vertical is observed. The concentration of radon decreases from 157 dpm/m³ at sea level to 35 dpm/m³ at about 3·7 km altitude, suggesting a vertical turbulent diffusion coefficient of ∼6×10⁴ cm²/sec. In contrast, the near absence of vertical gradient of radon in the monsoon air mass indicates that the vertical turbulence is much stronger during the monsoon period.

K-Ar ages of a number of samples from Rajmahal and Deccan Traps and from basaltic dykes of Gondwanas have been measured. The results suggest that the Early Rajmahals erupted in the middle of early Cretaceous (∼ 110 my) and probably continued to be active till the end of Cretaceous. Deccan activity started in Gujarat-Kathiawar area in Early Paleocene and spread over almost the entire area in next 5–7 my. However, in the north-eastern region of the traps around Chindwara and Amarkantak, the basalts were laid in the middle of the Eocene (∼ 47 my). The measured ages of Deccan dykes suggest a subdued hypabyssal activity continuing till the end of Eocene or beyond.

The K-Ar ages of Gondwana extrusions exhibit contemporaneity with Deccan activity even for the dykes which are located right close to the Rajmahal outcrops; indicating no regular drift of the foci of volcanic activity. A distant dyke from Cuttack gives an early Rajmahal age, and therefore probably indicates the vast extent to which Rajmahal activity manifested itself.