An Attempt to Point out, in a Concise Manner, the Advantages Which Will Accrue from a Periodic Review of the Variation of the Magnetic Needle, Throughout the Known World; Addressed to This Royal Society by William Mountaine and James Dodson, Fellows of the Said Society, and Requesting Their Contribution Thereto, by Communicating Such Observations concerning It, as They Have Lately Made, or Can Procure From Their Correspondents in Foreign Parts