506 TRANSACTIONS OF SECTION 4. 
the comparatively short period of nineteen years, so ably advocated by the late 
Mr. H. C. Russell, Government Astronomer of New South Wales, disappeared 
when testing multiples of that period, and that fifty-seven years more correctly 
represented the true period in Australia. It was, however, ascertained from a 
curve computed from the record of the Nile floods, which were at that time 
available, namely from A.D. 1736 to A.D. 1905, that the Nile’s period would 
appear to be either 114 or 171 years. . 
These conclusions were based on the results arrived at by discarding the old 
system of plotting the rises or falls above or below an arithmetical mean of 
the figures constituting the record, and adopting a system which would show the 
cumulative effect of the departures from the mean. Slow, persistent rises or 
falls which are not discernible under the old system are immediately detected 
by this method. 
The Nile’s period then arrived at was so long that it extended far beyond 
the limits of all rainfall records, except, perhaps, that of British rainfall, com- 
piled by the late Mr. Symons, F.R.S., and the Paris and Padua records, all 
three of which are more or less unreliable. There was consequently no means 
of proving its reliability or otherwise unless by comparing it with tables of 
histos1cal events, which was hardly admissible in an investigation of this nature. 
Fortunately the records of the height of the annual flood on the Nile from 
the years A.D. 641 to A.p. 1451 have recently been made available. In his letter 
to the author, forwarding a copy of this historical record, Mr. J. I. Craig, M.A., 
F.R.S.E., Director Meteorological Service, Cairo, stated that, although there 
is internal evidence of clerical errors in the Arabic records from which he 
extracted the gauge readings, on the whole he believes them to be trustworthy. 
With this assurance the author computed a series of residual mass curves 
derived from the means of most of the periods which have been propounded from 
time to time. None of these were satisfactory, with the exception of the curve 
derived from the means of successive complete periods of 76 years, of which 
there are ten altogether out of the whole record of 810 years. 
An inspection of the diagram will show that the conformation to a 76 years’ 
period is very remarkable, even when this period is extended up to the present 
time. Notwithstanding that there are two breaks in the records from 1451 to 
1825 of 285 and 25 years, respectively, the curve derived from the recent records 
still shows a similar conformation. 
From an historical point of view the diagram is an extremely interesting one. 
It represents the longest continuous record in the world. The dry and wet 
periods are clearly defined, ranging from nineteen to fifty-seven years of 
accumulated rise or fall with reference to the mean. 
The author was severely criticised during the discussion on his paper of 
July 1, 1910, previously referred to, for seeming to connect Halley’s comet in 
some way with ‘the weather.’ This was because he had drawn attention to the 
fact that the comet’s mean period was approximately 76 years, and also that its 
appearance seemed to occur during periods of great drought. 
The position of the comet at the time of its perihelion passage is shown on the 
diagram on fourteen occasions from information kindly supplied by Mr. C. I. 
Merfield, F.R.A.S. It will be seen that in almost every instance the comet made 
its appearance during the periods of greatest drought in Egypt. 
4. Imperial College of Science and Technology: The Goldsmiths’ Com- 
pany’s Extension of the City and Guilds (Engineering) College. By 
Professor W. E. Datsy, F.R.S., M.Inst.C.H. 
This papergave a concise history of the development of the City and 
Guilds (Engineering) College. The College was founded by the City and 
Guilds of London Institute in 1884, and its federation with the Imperial 
College of Science and Technology took place in 1907. In 1885 there were 35 
students in attendance; last session (1912-13) there were 570. 
After referring to previous extensions the paper gave a detailed account 
of the present engineering extension, named after the Goldsmiths’ Company, 
who have undertaken to defray the cost of erection. This extension includes 
