346 Notes and Comments. 
round the coasts of Great Britain were taken by the Ordnance 
Survey in 1859, but they were carried over much too short a. 
period to enable any conclusions to be drawn as to earth 
movements. There exist some fifteen recording tide-gauges 
round the coast of Great Britain, but as they are installed to 
obtain tidal records for navigation purposes, no great degree 
of accuracy is required, and it is probable that the work of 
reducing their records to mean sea-level would not be justified 
by results. 
The determination of the relative value of the height of 
mean sea-level as determined by levelling between the different 
gauges was carried out in 1860, but it is possible that. there 
may be an error of a foot -in the determination of the height 
of the zero of a tide-gauge as compared with Ordnance datum,. 
and there may also be an error of a foot in the determination 
made by the Ordnance Survey of the height of mean sea-level 
as compared with the zero of the tide-gauge. The values of the 
height of mean sea-level above Ordnance datum varied from 
o to nearly 2 feet, with an average of -65 feet above. These 
variations. are about what-is to be expected from errors of 
observation, and do not afford any evidence that mean sea- 
level is not constant round our coasts. 
THE BISHOP’S STORTFORD HORSE. 
We have previously referred to the fact that the so-called pre- 
historic horse found by the Rev. Dr. Irving at Bishop’s Stortford 
was probably quite a modern beast. Dr. Irving, however, has 
dug further, and tells us that ‘a considerable addition was made 
to previous prehistoric “ finds,’’ and a Holocene molluscan fauna 
was discovered in the bog silt. The silt was in places strewn 
with shelly débris, and it was only with the greatest care that 
complete specimens could be secured for identification. Of 
these, the following have been identified by Mr. B. B. Wood- 
ward, F.G.S., of the British bidentata Museum* (Nat. Hist.) : 
Helix nemoralis, Hygromia (Helix) hispida, Vitraea mitidula, 
Succinea putris, Pyramidula rotundata, Helix arbustorum. 
Clausilia was, I think, also found, but unfortunately got crushed 
at the Museum before it was identified. A small bivalve was 
fairly frequently met with, which I have identified at the 
Jermyn Street Museum as Pisidium. Of the fossil {sic} shells 
mentioned above, it may be pointed out that six at least of 
them have been noted in the Holocene deposits at Staines ; 
six have been described from the Barnwell Gravels; and 
three are described by. Von Hauer as characteristic of the 
diluvial loess of the Rhine and the Danube.’ Reasoning from 
the geological data, Dr. Irving ‘was led-at an early stage of 
* We have never heard of this particular institution, but it is so des— 
cribed by Dr. Irving.—ED. 
Naturalist, 
