248 REPORT—1857. Te 
from the great depth. From this has to be deducted the expansion of the 
cast-iron towers, which will amount to } an inch. 
The same deflection of course indicates the effect of 3 tons per foot on the 
bridge, as this weight produces 5 tons per inch strain on the cable. One foot 
per ton all over will therefore cause a deflection under 1 inch. 
C. 
In the design for the proposed Londonderry Bridge, ornamental cast-iron 
towers are proposed. As a mechanical question, we must estimate them as 
cast-iron columns acting simply to carry weight, which, ifthey were sodesigned, 
would be as follows :— 
The weight to be supported by the high tower when the bridge has its 
extreme load, is 1500 tons. To give 4 tons per inch, we require 375 inches, 
or 3750 lbs. per yard. 
The high towers being 30 yards high, the weight of metal will be 50 tons. 
The low tower will have 1320 tons with a full load, 122° = 330 inches, or 
3300 Ibs. per yard; the height being 20 yards, the weight will be 20 tons. 
The mean of the two towers will require for direct strain 40 tons. Add 
50 per cent. for bolts and ineffective material, 20 tons=60 tons. 
D. 
Estimate of the Weight of Suspension Bars. 
The weight to be carried is 1100 tons, if we allow 5 tons per inch; the 
section required is 220 inches, or 2200 Ibs. per yard; the average length is 
10 yards, and weight 10 tons. Add 50 per cent. for ineffective metal 5 tons 
=15 tons. 
Evidences of Lunar Influence on Temperature. 
By J. Park Harrison, M.A. 
fA Communication addressed to Major-General Sanine, General Secretary to the British 
Association, and ordered to be printed among the Reports. ] 
A FALL in temperature haying been found to recur with some frequency — 
between @ and ), and a corresponding rise shortly after ), tables and 
curves were formed in the early part of 1857, for a series of lunations, and 
a careful comparison instituted between the temperatures of the days at 
the period of suspected action. The result of the inquiry was satisfactory. | 
It appeared beyond question that decided effects (depending on lunar in- 
fluence) occurred at the time referred to; and even that a single day—the 
third before },—was on the annual mean of considerably lower tem- 
perature than another day, viz. the second after ) ; the difference between 
the two temperatures being by far the greatest in the winter months. These 
facts I had the pleasure of communicating to you soon after they had been 
ascertained ; and they were shortly afterwards laid before the British Asso- 
ciation at Dublin. 
The following Table was then formed of the mean annual temperatures 0 
eight fixed days, viz. the third before and the second after the four principal 
phases of the moon in each lunation, for 21 years. The observations chiefly 
used were those made at Dublin under the direction of the Ordnance Survey 
in 1836-1852, and were well adapted to my purpose from being collected 
in a single volume; the remainder were from the Greenwich results of 
1852-1857. 
