AN INTERESTING FIND.

Evening Post, Volume LXXX, Issue 4, 5 July 1910, Page 10

AN INTERESTING FIND.

DIATOMACEOUS EARTH

£SY TELBGBAPH — SPECIAL TO THE POST.] CHRISTCHURCH, This Day. Mr. R. Speight, assistant curator of CanterbuTy Museum, has received from Middlemarch, Otago, some interesting specimens which are now displayed in tlie case set apart for fresh exhibits in the museum. They are pieces of diatomacoous earth, which it is reported came from a deposit covering about. 120 acres with a thickness of 70 feet. Mr. Speight states that if this is so the deposit will evidently rank as one of the most important in the world. Large deposits are found in other places, notably New Jersey, where there is an area of three acres with a thickness from one foot to three feet, and another deposit of not less than 300 -ieefc in thickness is reported, but apparently it does not cover anything like the same area. Steps have been taken already to make use of the deposit, and 385 bags have been sent to England. Unfortunately the deposit is not very accessible and is somewhat remote from the railway. The earth is really whitish or buff coloured powdering rock, composed mainly of shells of umicellular plants of microscopical dimensions called} diatoms. Deposits of this material are forming now in many •places, notably at the bottom, of lakes and swamps. They were also kid down occasionally in former geological times. Thick and extensive beds occur in New Zealand near Middlemarch, Oamaru, and Auckland, and smaller deposits are foui.d in many other places. The Oamaru deposits are amongst tlie richest in tho world. These tiny plants are frequently found in the sands 1 at New Brighton, near Obristcburch, and in 1882 ; n «stensiv* deposit was reported when workwas being done in the swamp in connection with the roads near New Brighton. On account of their miscroscopie interest and geological importance diatoms acquired an unusual share of scientific and even popular attention. They were discovered in 1702, and their movements there noted 80 years later, but their thorough investigation became possible only with the development of the compound microscope. According to one authority diatoms live in enormous abundance at the surface of the sea in cold temperate and arctic latitudes and the mud of the sea bottom is very often composed largely of the shells of dead diatoms which are falling from the surface in gen-tle but unceasing rain. Diatomaceous earth is used as a polishing powder, as an obsoTbent for nitroglycerine in the manufacture of dynamite, as a non-conducting material in connection with boilers and for siliceous glazed paints.