VII. RADIOACTIVITY IN GEOLOGY AND COSMOLOGY 1. RADIOACTIVITY OF ROCKS AND MINERALS The researches of Elster-Geitel, showing that the electrical conductivity of underground air was greater than that of atmospheric air and tracing this excess to the presence of Rn (86Ra) and Tn (86Th), led to searches for radioactive materials in air, underground gases, rocks of all forms and various natural waters. An early review of work in this field is that of Heimann-Marckwald. The investigations of the radioactivity of rocks by Strutt, Joly, Holmes,1 Büchner and others have led to certain general conclusions in regard to the quantities of radium and thorium in rocks of various classes. It is found that igneous rocks contain proportionately larger quantities of radium than sedimentary rocks. Büchner gives the average radium content of the former as 0.04 × 10-10 gm/gm rock and that of the latter as 0.015 x 10-10. Strutt drew attention to the fact that acidic rocks have a larger content of radium and thorium than basic rocks. Joly 2 in a recent communication gives the following values for the uranium content (from the radium equivalent), the thorium content and the ratio of these in various rocks: The Th/U ratio is nearly 2 and its constancy is perhaps of some signifi cance (cf. Kirsch). Besides the many older analyses there are more recent ones by Sahlbohm, Serra, Smeeth-Watson, Holmes,2 Poole and Karl-Lombard. The lavas from various volcanoes have been studied particularly by Joly 1 and Fletcher. The radium and thorium contents vary with the volcano and they are greatest for lava from Vesuvius, the radium content of which is 0.16 × 10-10 gm/gm lava and the thorium content, 4.1 × 10-5 gm/gm lava. In general the radium and thorium contents of lavas are greater than for igneous rocks. Trovato studying the radioactivity of the solid products from Etna concludes that all show some radioactivity, and lists them as follows in order of increasing activity: Lava recently ejected, compact lava, scoria, gravel, old lava, basalt, cinders, mud of thermal springs, tufa, vegetable loam. The radioactivity of Trovato's samples seems to diminish with increase of depth of origin, in agreement with Büchner's findings for samples of sandstone from borings. Büchner and Fletcher have drawn attention. to the fact that rocks which are different petrographically and chemically, if from one locality, have roughly the same radium content, while if from. widely different localities they may be very different in this respect. For example, the mean radium content of rocks from the Andes is 0.008 × 10-10 gm/gm rock, from the British Isles, 0.015 × 10-10, and from Central Europe, 0.05 to 0.07 × 10-10. The pitchblende of Bohemia is very much. richer in radium then the carnotite of America, although both are sufficiently rich to be commercial sources of radium. The results of previous investigations have been collected and reduced to common units by Büchner and by Gockel. More recent papers are those of BaltuchWeissenberger on monazite sand, of Bamberger-Weissenberger on pyromorphite, of Ellsworth on pegmatites of Ontario, of Francesconi-GranataNieddu-Angelino on Italian minerals, of Hirschi on Swiss minerals and rocks, of Kithil on monazite, of Pratt on allanite, of Schoep on various minerals, of Vernadsky on mendeljevite, of Walker-Parsons on ellsworthite, of Aartovaara and Laitakari on minerals of Finland, of Yajnik-Kohli on minerals of India. It is of interest to note the finding of von HevesyJantzen that zirconium ores with a large thorium or uranium content also contain rather large amounts of hafnium (72), the radioactivity of zircons running roughly parallel to the hafnium content. Pollux, a caesium mineral, shows, according to Hoffman, no radioactivity. Quirke-Finkelstein measured the radium content of 16 stony, and 7 iron meteorites. The mean radium content of the stony meteorites was 7.39 × 10-13 gm/gm. Including the value for the only other stony meteorite previously measured (Strutt) the average becomes 7.61 × 10-13. Two of the iron meteorites gave a mean of 6.88 x 10-13 while the other five showed no radioactivity. Strutt found the single iron meteorite which he investigated to be inactive. 2. RADIOACTIVITY OF WATERS J. J. Thomson and Sella-Pocchettino independently discovered in 1902 that natural waters are radioactive. The radioactivity is due to radium or thorium dissolved in the water, and to Rn (86Ra) and Tn. (86Th) absorbed in the water as well as that being produced from radio-elements in solution. The radioactivity may be acquired either at the primary source or from the rocks and minerals through which. the water passes, and may be affected when the water mixes with other waters. In general, cold mineral springs from granite are more radioactive than those from sedimentary rocks. Cold sulphur springs are but slightly radioactive. At Bagnières-de-Luchon, Lepape finds deep springs having high temperature and high sulphur content to be nonradioactive, cold or tepid surface springs with no sulphur to be highly radioactive. In Japan some sulphur springs are almost inactive while Zuihôzi a mineral spring (temperature above 31° C) in Arima, has a Rn (86Ra) content of 138 × 10-10 curie/liter and the Murasugi Mineral Spring (25° C), 160 × 10-10. The radioactivity of the wells bored at Heidelberg increased with their depth, being 0.01 x 10-10 curie/liter near the surface and 0.97 × 10-10 at a depth of 590 meters, according to Eblervan Rhijn. Perret-Jaquerod examined the radioactivity of the thermal and mineral springs in the Jura district and found it to vary in a marked manner from southeast to northwest across the axis of the Jura Mountain chain. In Czechoslovakia, in the region of the pitchblende mines, the Grubenwasser Spring in Joachimsthal has (Gockel) a Rn (86Ra) content (the highest known) of 7450 x 10-10 curie/liter, while at Carlsbad the content of the Mühlbrunnen Spring is 113 × 10-10 and that of the Sprudel Spring only 0.036 × 10-10. These variations are due, no doubt, to differences in the geological formations where the waters originate and through which they pass. Variation in the Rn (86 Ra) content has been observed in the same spring at different times of the year. Among the older observations of this kind are those on springs at Teplitz-Schönau (Hauser) and at Wiesbaden (Henrich). Ramsey studying radioactive springs in Indiana, found that there was an increase in the Rn (86Ra) content of the spring waters following a season of rain and a decrease after continued dry weather. Similar changes have been noted by Krüse, Loisel1 and Ludewig,1 while Steichen reported the opposite type of change for the hot springs at Tuwa (India), attributing the anomaly to local conditions. Ludewig 2 observed for the Trinkquelle in Brambach (Saxony) that the amount of Rn (86 Ra) decreased with the increased use of water from the well. Loisel,2 studying the springs at Bagnoles-de-l'Orne, came to the conclusion that some emanation (86) coming from deep sources, through granite, is constant in amount, while other emanation coming from superficial layers is affected by rains. Loisel also observed that a relation exists between the radioactivity of the springs and the geological structure of the neighborhood. Large variations have been noted. in the radioactivity of springs at Orsovo (Roumania) by Loisel-Michaïlesco; there each spring showed great variations from day to day. Eve reported an increase in the radioactivity of the St. Lawrence River during floods over that in dry seasons. Some attention has also been given to the relation between the Rn (86Ra) content and the temperature of springs in a given region. Isitani-Yamakawa concluded that the decrease in Rn (86Ra) content with the rise in temperature is not altogether due to a decrease in the absorption coefficient of the gas in the water, but that the surface layers through which the originally active water permeates play an important rôle. Isitani, Isitani-Manabe and IsitaniYamakawa have generally reported the chemical analysis of the water or of its residues. Similar data have been given by Cluzet-Chevallier, who call attention to the only French spring (Echaillon) furnishing RdTh (90ThII) for therapeutic purposes; by Pouget-Chouchak, who classify the radioactive baths of Algeria according to the chemical analyses of the waters; by Becker and Henrich,' who studied iron springs; by Lepape,1 who gave attention to the temperature and sulphuration of the springs at Bagnières-de-Luchon; by Lester who made tests for Tn (86Th) as well as for Rn (86Ra) in the springs of Colorado in regions where monazite sand is common, but who found only one spring to contain Tn (86Th); and by Lepape2 who also measured the Tn (86Th) content of springs in the Pyrenees. Examinations of the springs in various countries have been made by many investigators. Papers on the subject have been listed by Gockel and by Meyer-von Schweidler. Papers by the following authors, besides those more specifically referred to in this section should be mentioned for the sake of completeness: Ikeuti, Hemmeter-Zeublin, Elworthy, Okaya, Henrich, Nasini-Porlezza, Viola, Moureu-Lepape-Moureu. Various units have been used for reporting Rn (86Ra) content, viz., the curie/liter (the standard unit), including its various subdivisions; the mache unit, the e. s. u. of current/liter due to the a-rays of Rn (86 Ra) alone; the uranium unit, where calibration has been made by means of the Rn (86Ra) from pitchblende of known uranium content; the mg. min, i. e., the Rn (86Ra) produced per min per mg Ra (88Ra) per unit volume (generally 10 liters) used by some of the French writers; and the eman. Reduction to the standard unit, the curie/liter is effected by the use of the following conversion factors (M.-S., Meyer): From the enormous number of springs the Rn (86Ra) contents of which have been reported, data regarding a few are presented in Table VII, selection being based upon geographical distribution, Rn (86Ra) content, temperature, and importance as judged by the spring's reputation; the list is necessarily very limited. The methods used in determining the Rn (86Ra) content have differed considerably. The original methods for expelling the gases were by bubbling air through the water, and by boiling it. Various forms of shaking apparatus have also been used. These and other methods are discussed by Gockel, Meyer-von Schweidler, Greinacher, Nürnberger and Ludewig. The radioactivity of tap-waters varies from 0.025 to 1.4 × 10-10 curie/ liter. One would expect very much the same radioactivity here as in ordinary spring and river waters. The radium content of such waters is of the order of 0.005 × 10-10 gm/liter. Folmer-Blaauw report negligible radium content in the water of Lake Rochanye (Isle of Voorne near Hook of Holland) although the sediments in the lake are radioactive. Sea water from all parts of the world was tested for Rn (86Ra) and for radium content at an early date. The Rn (86Ra) content (Knoche, Laub) of the Pacific Ocean is considerably less than that of the Atlantic Ocean, the mean values being, for the former 0.23 x 10-10 curie/liter and for the latter 0.47 × 10-10. The radium content in the Atlantic Ocean varies from 4× 10-15 gm/gm east of Pernambuco to 14 × 10-15 in the Gulf Stream and to 34 × 10-15 off the coast of Ireland (Joly). It is of interest to note that Hewlett, who studied the sea salt from samples of water taken far from land during the expedition of the Carnegie (1915-1917), found by Joly's method (fusing the salt with sodium-potassium carbonates at 1000° C) no evidence of Rn (86Ra). 3. RADIOACTIVITY OF THE ATMOSPHERE AND OF The Rn (86Ra) content of the atmosphere is of the order of 10-16 curie/cm3, the amount varying with the location and meteorological conditions. The Rn (86Ra) content over land varies from 20 to 125 × 10-18 curie/cm3. The content over the ocean decreases with increase of distance from land and is very low in subantarctic latitudes, being, according to the measurements on the Carnegie, cruise of 1916, (Baueret al.) 3.3 x 10-18 curie/cm3 over the Pacific Ocean and 0.4 × 10-18 over the Subantartic. It is considerably greater over the Atlantic Ocean. It is greater above dry soil than above moist soil, greater above cultivated than above compact soil, and practically nil over snow (Olujič, Huber). The diurnal and seasonal variations and those dependent upon meteorological conditions and elevation above ground level have been studied by Allen, Blackwood, Huber, Jacot, Olujič, von Schweidler, WrightSmith, Swann and Zlatarovic. The methods used were the collection of active deposit on wires and absorption by charcoal. Allen found that even uncharged or positively charged wires collected radioactive material from the air and that the amount so obtainable increased when the |