He evinced the same spirit in respect to the geological survey. As his mind was not satisfied, he would not make known his results to the Legislature. They demanded the report, and he asked for an extension of time. Thus he continued his labors from year to year, upon a stipend scarcely adequate to cover his expenses. Instead, however, of nearing the goal, he only receded from it. New difficulties met him in the work; fresh questions arose, in the progress of geology itself, that called for reëxaminations. His notes swelled to volumes, and his specimens increased to thousands. He was in danger of being crushed under the weight of his doubts and his materials. At last, the people clamored for the end of the work. The Legislature became peremptory, and forced Percival to acquiesce. In 1842 (seven years from the commencement of the survey) he rendered an octavo report of four hundred and ninety-five pages, in the introduction to which he observes,--"I regret to say, I have not had the means allowed me for additional investigations, nor even for a proper use of my materials, either notes or specimens. The number of localities from which I have collected specimens I have estimated at nearly eight thousand; the records of dips and bearings are still more numerous. The report which follows is but a hasty outline, written mainly from recollection, with only occasional reference to my materials, and under circumstances little calculated for cool consideration. It was written, however, with an intention to state nothing of the truth or probability of which I did not feel satisfied. None can regret more than I do its imperfection; still I cannot but hope that it will contribute something towards the solution of the problem of the highest practical as well as scientific importance, the exact determination of the geological system of the State." Of this remarkable production it may very briefly be said, that it will ever remain a monument to the scientific and literary powers of its author. It describes every shade of variation in the different rocks, and their exact distribution over the surface of the State. This it accomplishes with a minuteness never before essayed in any similar work. The closeness and brevity of his descriptions make it one of the dryest productions ever issued on geological science, scarcely omitting the work of Humboldt, in which he sought to represent the whole of geology by algebraic symbols. Percival's work actually demands, and would richly repay, a translation into the vernacular of descriptive geology,--the language and mode of illustration employed by Murchison and Hitchcock. In its present form, it is safe to say, it has never found a single reader among the persons for whose benefit it was written.