Description
A sargasso detector is a complex device. Set upright on a base of fine mahogany are two bands of gold that intersect at 90°. Each band is 10 inches in diameter, 1 inch wide and 0.5 inch thick. Engraved around each band's circumference are tiny magical runes of great complexity. The base upon which the golden bands stand is rectangular: 1 foot long by 1 foot wide, and 2 inches thick. At each corner of the base, set vertically, is a thin spindle of silver-gold alloy, about 0.25 inch thick and 12 inches long. Within the intersecting golden bands, hanging from the upper point where they meet, is a needle of platinum, suspended horizontally by a single human hair attached to its midpoint.
Powers
Based on the magical and technological theories promulgated by the silver dragons of Edill, the sargasso detector allows spelljammers to avoid the dangerous sargassos - magic-free zones - found in many crystal spheres. The detector can sense the presence of a sargasso at a range of one million miles (1.6 million kilometers). When the device is within range, the four alloy spindles begin to vibrate rapidly, causing a soft, high-pitched hum, and the suspended platinum needle rotates until it is pointing in the direction of the sargasso.
The detector does not indicate the distance to the sargasso; neither the volume nor the pitch of the humming varies with distance. If the ship is heading directly toward the sargasso, then the needle points directly toward the vessel's bow. If the ship is moving laterally relative to the sargasso, the needle will slowly rotate so that it continues pointing directly at it. From the speed with which the needle is rotating and the speed of the vessel, it is possible to calculate the distance to the sargasso.
History
The first sargasso detector was created one hundred years ago by the elven mage Thalia, after a protracted visit with the silver dragons of Edill. Since then, many other mages throughout the universe have learned how to replicate her cunning creation. Nevertheless, the demand for these items is much greater than the supply.