1920.] Morgan.' — -The Tertiary Beds of Central Otago. 
33 
wood, leaves, &c.), together with the fossils in the overlying lake-muds, 
should be carefully studied. A detailed geological survey of Central Otago 
is justified from an economic point of view by the quartz drifts alone, to 
say nothing of the other mineral possibilities of this region. 
Literature. 
Barrell, Joseph, 1912. Criteria for the Recognition of Ancient Delta Deposits, Bull. 
Geol. Soc. Am., vol. 23, pp. 377-446. 
Cotton, C. A., 1919. Problems presented by the Notocene Beds of Central Otago, 
N.Z. Jour, of Sci. and Tech., vol. 2, March, 1919, pp. 69-72. 
McKay, Alex., 1884. On the North-eastern District of Otago, Rep. Geol. Explor. 
during 1883-84, No. 16, pp. 45-66; and On the Origin of the Old Lake-basins of 
Central Otago, same vol., pp. 76-81. 
- 1894. On the Older Auriferous Drifts of Central Otago, Pari. Paper C.-4; 
second edition, 1897 (issued in a different form). 
Marr, J. E., 1898. The Principles of Stratigraphical Geology. 
Marshall, P., 1912. New Zealand and Adjacent Islands (reprinted from Handbuch 
der regionalen Geologie, Bd. 7, Abt. 1, Heidelberg). 
-1918. The Geology of the Tuapeka District, N.Z. Geol. Surv. Bull. No. 19. 
Morgan, P. G., 1914. The Waikaka Gold-mining Field, Eighth Ann. Rep. N.Z. Geol. 
Surv., part of Pari. Paper C.-2, pp. 147-52. 
Morgan, P. G., and Bartrum, J. A., 1915. The Geology and Mineral Resources of the 
Buller-Mokihinui Subdivision, N.Z. Geol. Surv. Bull. No. 15. 
Park, James, 1906. The Geology of the Area covered by the Alexandra Sheet, N.Z. 
Geol. Surv. Bull. No. 2. 
- 1908. The Geology of the Cromwell Subdivision, N.Z. Geol. Surv. Bull. No. 5. 
-1910. The Geology of Neiv Zealand. 
THE ORIGIN OF NEW STARS: THE DYNAMICS OF 
CELESTIAL ENCOUNTERS. 
By A. C. Gifford. 
Since collisions amongst the stars play an important part in the evolution 
of the universe, it is interesting to consider numerically and illustrate 
graphically the details of the approach to such an encounter. The chief 
points to consider are— 
(i.) The forces in action ; 
(ii.) The velocity and kinetic energy acquired in reaching any definite 
distance from the centre of attraction ; 
(iii.) The time occupied on each stage of the journey ; 
and, when the motion is not rectilinear,— 
(iv.) How the nature of the orbit depends on the initial circumstances 
of the motion; 
(v.) Whether the attracted bodies, in any particular case, will ultimately 
collide or pass by one another ; and 
(vi.) What happens when a collision does occur. 
3—Science. 
