About a week ago I had the pleasure of meeting Dr. Blanchard during a History of Medicine Lecture Series steering committee meeting. Dr. Blanchard donated one of the first sets of materials in an on-going donation to the archives. This accession was composed of materials he used for his presentation on Iceland Spar that was given at the November meeting of the Northwest Independent Scholar Association. The panels from the presentation were displayed at the Casey Eye Institute for a while as well.
|The presentation panels|
Iceland Spar, also called Optical calcite, is a crystal formed of calcium carbonate (CaCO3) and was found initially in Iceland, however, functional mines all over the world have developed since its discovery.
Blanchard’s research begins with Erasmus Bartholin who wrote the first scientific description of the Iceland Spar, but who also concluded much work was yet needed to understand the properties of light based on his observations of the spar. Blanchard’s research then touches on the work of Christiaan Huygens, a Dutch scientist, whose work focused on light refraction. Huygens tested his theories on the Iceland Spar, and concluded that more work was needed to understand light. Blanchard notes that Huygens’ theories did not gain much traction at the time.
|Discussion of Newton's theories|
|A breakdown of the mineral properties of calcite|
However Newton’s theories did. Newton’s theories of light which were not debunked due to the nature of the Iceland Spar were widely accepted for over a century
Here’s a closer look at the “dual” nature of the spar:
|The calcite sitting over the text, note the doubling effect|
For more detail about the history of calcite and the theories of light that surround it, please visit the Historical Collections & Archives.