Table 1—SAMPLING STATIONS Rainfall Soil Altitude 1954-1956 in./yr pHs Ref. Locality Al A2 A3 Cwmystwyth, Cardigan Cwmystwyth, Cardigan Cwmystwyth, Cardigan 1200 1100 800 60 60 60 4.3 4.5 4.9 0.14 0.17 1.0 Peat on shale Soil, grass, (free draining) sheep bone Peat on shale Soil, grass B Vyrmwy, Montgomery 1100 62 5.4 1.8 Peat on shale Soil, grass, 2.7 (free draining) Free draining soil on sand- sheep bone Soil, sheep bone Cc Talgarth, Brecon ft Total Ca, 1050 36 6.2 g/kg Type (free draining) Samples stone D Princetown, Devon 1300 81 5.6 5.8 Sandy peat Soil, grass, E Rookhope, Durham 1600 42 3.6 0.4 Peaty sandy Soil, grass, F Norwich, Norfolk G Boxworth, Cambs, 85 26 7.5 4.7 157 22 6.8 14.6 on granite loam with podsol layer Sandy loam with gravel Dark brown loam with H Aldermaston, Berks. 250 25 6.0 1.6 I Culham, Oxon 180 22 6.6 3.0 chalk Sandy soil with humus Sandy soil sheep bone sheep bone Soil, grass, sheep bone Soil, grass, sheep bone Soil, grass Soil, grass on lower J K Grove, Berks. Chilton, Berks. 250 400 25 7.1 24 39 8.0 156 greensand Heavy gault clay Calcareous clay with Spee ecoe lay Soil, grass Soil, grass flint test the penetration with depth. At A3 one single square yard soil sample only was taken in May, but when the sampling was repeated in November, twelve cores were taken. At the five auxiliary stations, repeated samples of grass were taken at intervals from May to September 1956. Samples were of two types: (1) Accumulated growth taken from previously untouched plots; (2) Fresh grass which had grown since the last cutting. 4 RESULTS ON SOIL, GRASS AND SHEEP BONE 4.1 Sr®° in Soil A list of the results of Sr°® analysis of soils taken in 1956 is given in Appendix 1, anda summary of the results by HCl extraction is given in columns 3 to 5 of Table 2. In Fig. 4 the sr*? activity by HCl extraction per unit area of soil to depth 4 in.* is compared with the annual rainfall at the samestations in the years 1954-1956. The line on the graph showsthe fallout of Sr*° which would have occurredif it is proportional to rainfall, using as reference point the cumulative total in rain of 5.6 mc/km? to July 1956, measured at Milford Haven, where the annual rainfall is 38 in. (Stewart et al., 1956, extended by further measurements). There isa rather large scatter in the results from the stations Al, A2 and A3, but otherwise there is good agreement between the fallout of Sr*® believed to have occurred in rain, and that found in the top 4 in. of soil. *The unit puc/m* is used in Table 2 and Appendix 1. The unit mc/km’, equivalent to 1000 puc/m? is used in Fig. 4, because this unit is a commonly used measure of fallout generally. 213