1.0Tour ELhttp://www.edisontc.org/lightingadminhttp://www.edisontc.org/lighting/author/admin/rich600338<blockquote class="wp-embedded-content" data-secret="NOuqPAL789"><a href="http://www.edisontc.org/lighting/2016/04/12/caving-lamp-technology/">Caving Lamp Technology</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="http://www.edisontc.org/lighting/2016/04/12/caving-lamp-technology/embed/#?secret=NOuqPAL789" width="600" height="338" title="“Caving Lamp Technology” — Tour EL" data-secret="NOuqPAL789" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script type="text/javascript"> /* <![CDATA[ */ /*! This file is auto-generated */ !function(d,l){"use strict";l.querySelector&&d.addEventListener&&"undefined"!=typeof URL&&(d.wp=d.wp||{},d.wp.receiveEmbedMessage||(d.wp.receiveEmbedMessage=function(e){var t=e.data;if((t||t.secret||t.message||t.value)&&!/[^a-zA-Z0-9]/.test(t.secret)){for(var s,r,n,a=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),o=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),c=new RegExp("^https?:$","i"),i=0;i<o.length;i++)o[i].style.display="none";for(i=0;i<a.length;i++)s=a[i],e.source===s.contentWindow&&(s.removeAttribute("style"),"height"===t.message?(1e3<(r=parseInt(t.value,10))?r=1e3:~~r<200&&(r=200),s.height=r):"link"===t.message&&(r=new URL(s.getAttribute("src")),n=new URL(t.value),c.test(n.protocol))&&n.host===r.host&&l.activeElement===s&&(d.top.location.href=t.value))}},d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",function(){for(var e,t,s=l.querySelectorAll("iframe.wp-embedded-content"),r=0;r<s.length;r++)(t=(e=s[r]).getAttribute("data-secret"))||(t=Math.random().toString(36).substring(2,12),e.src+="#?secret="+t,e.setAttribute("data-secret",t)),e.contentWindow.postMessage({message:"ready",secret:t},"*")},!1)))}(window,document); /* ]]> */ </script> http://www.edisontc.org/lighting/files/2016/04/Knox700.jpg700466A Brief History of Caver’s Light Sources: In early times—even pre-historic—hand-carried torches were commonly carried by cave explorers. At Mammoth Cave, Kentucky, reeds that grew along the Green River and tributary streams were dried and then set afire to provide light for paleo-Indians who explored sometimes miles into the cave in search of crystals and … Continue reading