PREFACE.

THE Transactions of the British Association consist of three parts; first, of Reports on the State of Science drawn up at the instance of the Association; secondly, of Miscellaneous Communications to the Meetings; and thirdly, of Recommendations by the Committees, having for their objects to mark out certain points for scientific inquiry.

It is proper to remark, that some of the Reports here printed are to be considered in the light of first parts of the intended survey of the sciences reviewed in them, the continuation being postponed to a future Meeting. Thus, the Report on Hydraulics, by Mr. G. RENNIE, will be completed in a second part, to be presented to the Meeting at Edinburgh; the Report on the mathematical theory of the same science, by the Rev. Mr. CHALLIS, which is here restricted to problems on the common theory of Fluids, will be further extended to the theories which have recently been advanced respecting the internal constitution of Fluids and the state of their caloric, to account for certain phænomena of their equilibrium and motion; and the Report on Analytical Science, by the Rev. Mr. PEACOCK, which in the present volume includes Algebra, and the application of Algebra to Geometry, is intended to be hereafter concluded by a review of the Differential and Integral Calculus and the theory of Series. In like manner, to the Report on Botany, by Dr. LINDLEY, which embraces only the physiological part of the science, that which Mr. BENTHAM has undertaken on the State and Progress of Systematic Botany will be supplemental; and to the present Report, by Dr. CHARLES HENRY, on one branch of Animal Physiology, a more general review of the progress of that science will be added by the Rev. Dr. CLARK.

With respect to the next part of the Transactions, which includes the communications made to the Sections, two