SECTIONAL TRANSACTIONS.—A. 349 
For a long time thrust bearings presented an insoluble problem until 
Michell conceived the idea of providing tapered films round the thrust 
annulus, each film generating pressure to support its own share of the load. 
Single-collar thrusts have thus superseded the old standard multi-collar 
thrust blocks which, on account of their flat parallel bearing surfaces, were 
very limited as regards their load-carrying capacity and gave constant trouble 
due to unequal expansion of shaft and block. 
The success attending the universal adoption of the single-collar thrust 
was followed by the utilisation of the same principle in important journal 
bearings. The solid top and bottom brasses are replaced by a series of 
tipping pads all round the journal which produce a ring of tapered oil films 
carrying a greatly increased unit load on a much shorter length of shaft. 
Good clean oil of a viscosity dictated by load and speed is essential for all 
bearings. When they have been standing for some time and have to be 
started up under load, the lubricant should possess sufficient inherent 
“oiliness ’ to ensure that however attenuated the film it shall ‘ persist’ 
between the loaded surfaces and refuse to be squeezed out entirely. This 
obviates metallic drag and wear at starting, the full pressure film being 
_ “struck ’ and maintained as soon as the shaft begins to revolve. 
Bearings designed, constructed and operated as above described run for 
years without any sign of metallic wear or renewal of parts. The oil is the 
only element that wears, and this is easily replenished or renewed as may be 
required. 
Dr. F. P. Bowpen; Mr. D. Ciayton; Dr. A. E. Dunstan; Mr. H. 
HIGINBOTHAM ; Miss M. Norttace; Mr. J. E. SOUTHCOMBE ; 
Dr. W. J. D. Van Diyycx. 
Dr. F. J. W. Wuippte.—Recent advances in seismology (12.0). 
Seismology has two principal objects: one is to utilise the records of 
waves travelling through the earth to determine the structure of the planet ; 
the other is to study the nature of earthquakes, their geographical distribu- 
tion, the depth of the foci, the conditions under which they occur and their 
relation to regional geology. 
The method of investigation of the waves is to utilise the records from 
Seismographs in all parts of the world. An effective way of doing this is to 
collect the seismograms of a particular earthquake and compare the details. 
In general it is simpler to make use of the bulletins which are prepared at 
the observatories. Such bulletins are collected at Oxford, where the 
International Seismological Summary is prepared. By this system the 
€picentres of all but the very small earthquakes can be located and the times 
of transmission of the seismic waves can be compared. One of the objects 
of Prof. Turner in starting the I1.S.S. was to provide material from which 
accurate tables of the average transmission times could be deduced. This 
material has been used with great skill and ingenuity by Dr. Jeffreys, who 
Was assisted in the most laborious part of the work by Mr. Bullen, and 
Dr. Jeffreys is now able to state that the tables are consistent to a second. 
This remarkable achievement would not have been possible if it were not 
for the precision of the readings of the seismograms. This precision is to 
_ be attributed not only to the excellence of the seismographs, but also to the 
facility with which clocks can be regulated by the use of broadcast signals. 
ismology owes much to wireless telegraphy. 
_ The number of recognised types of wave is now quite large: Jeffreys and 
