432 
‘ Transactions,’ read February 27th, 1745. “A description of an 
hygrometer.” A thin piece of sponge so cut as to contain as large a 
superfices as possible. This hangs by a fine thread of silk upon a 
beam, and is exactly balanced by another thread of silk strung 
with the smallest bird-shot at equal distances, and so adjusted as 
to cause the index to point at the middle of the graduated arch, 
when the air is in a middle state between the greatest moisture 
and the greatest dryness. 
In December of the same year he forwarded through his friend 
Baker a description of an improved “ weather cord.” This improve- 
ment displays considerable ingenuity. It consisted of a rack attached 
to the centre of the cord, on which worked a toothed segment fixed 
to the shorter arm of an index, the contracting and relaxing of 
the cord causing the index to rise and fall. 
On January 23rd, 1750, a splendid aurora was seen in Norwich 
and all over the county ; and Mr. Arderon sends the following 
minute description of it to the R.S. “ The wonderful appearance 
of the aurora borealis on January 23rd last, have been taken 
notice of in most parts of England, though in different forms. At 
Norwich, I believe, it was as extraordinary as at any place what- 
ever, but the weather being very cold, and myself being somewhat 
indisposed, 1 did not make all the remarks I could have wished ; 
the few I did make are as follows : — This wonderful aurora began 
at six in the evening, with a blackish cloud in the N.E., out of 
which sprung a sti'eak of scarlet coloured rays of a surprising 
beauty and vividness. This presently extended to within a few 
degrees of the s.w. horizon, passing directly through the zenith, 
and so continued near a quarter of an hour, when red and yellow 
columns began to rise upward from every quarter. At seven a 
black cloud rose up in the s.e. and quickly put on a semicircular 
form, with light yellowish vapours ascending out of its upper edge 
and representing a glory of uncommon brightness. At eight the 
black cloud was dispersed, but the yellow glory remained, and 
round that sprang up another circle of red which made the wholo 
appear very tremendous. The reddish streams, as well as this last 
mentioned circle, were sometimes so dense that the stars of the 
first magnitude could not be seen through them. The night was 
full as bright as it is when the moon is eight days old, but 1 could 
not compare it to neither the light of the sun nor moon, some of 
