Annotated list of references on Iceland spar and polarized light

-1936 Pollard, ?U.K. Usually, Nicol´s prisms are much smaller than this [i.e. 4” aperture]
and even moderately sized optically perfect crystals <strong>of</strong> the spar have already become
scarce.
-1936, South African Geological Survey: Iceland spar has, in the past, been obtained
almost exclusively from Iceland but owing to the falling <strong>of</strong>f <strong>of</strong> the production <strong>of</strong> good
optical grade material from that country and the increasing demand for the mineral,
attention has been directed to other possible sources <strong>of</strong> supply.
-1938 Griggs, U.S. … Iceland spar… difficult to obtain…
-1940 Kremers, U.S. Natural calcite <strong>of</strong> optical quality is scarce…..The acute shortage <strong>of</strong>
calcite in the larger sizes has for several years stimulated the search for a proper
substitute [he mentions sodium nitrate specifically].
-1948 Archard and Taylor, U.S. … more recently [i.e. after 1936], owing to the shortage
<strong>of</strong> calcite,…
- 1949 Evans, U.S. …Unfortunately calcite is so difficult to obtain [in large sizes] that its
general use in birefringent filters is probably impossible.
-1950 Schumann and Piller, D… Das Versiegen der natürlichen Vorkommen von
optischem Kalkspat bildet seit langem eine beständige Sorge aller beteiligten
Fachkreise…., [and] ...Kalkspatpolarisatoren, deren Beschaffung ständig schwieriger
wird…
- 1950 Hartshorne and Stuart, U.K. ... because large pieces <strong>of</strong> optical calcite are
practically unobtainable nowadays, and...
-1953 Rinne-Berek, 12 th ed. D… Da für optische Zwecke verwendbarer Kalkspat in den
letzten Jahren immer seltener geworden ist…
-1961 Zirkl, A … (summary <strong>of</strong> 1959 lecture) Hinzu kommt, dass die Beschaffung von
Kalkspat immer schwieriger und kostspieliger wird, weil die Vorkommen in Island
praktisch erschöpft sind.
-1967 Nester and Schroeder, U.S. Naturally occurring calcite <strong>of</strong> great purity has
gradually become more difficult to obtain as great use has been made <strong>of</strong> this material in
relatively recent years.
-1968 Ammann and Massey, U.S.…large natural [calcite] crystals <strong>of</strong> good optical quality
are becoming increasingly scarce.
Lensfield Cottage, Cambridge, 6 July, 1886.
To his Excellency, the Minister for Iceland, Copenhagen.
Sir,
As I hold the <strong>of</strong>fice <strong>of</strong> president <strong>of</strong> the Royal Society <strong>of</strong> London, the oldest scientific
society in this Kingdom, I hope your Excellency will excuse me for troubling you on a
matter <strong>of</strong> scientific importance, possibly also <strong>of</strong> some slight commercial interest to your
country.
This mineral known as calcite is much used by scientific men for instruments
employed in investigations and lectures relating to polarised light. This mineral is
common enough: but it has nowhere, to my knowledge, been found in large, clear,
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