7. In every case, if possible, the approximate _quantity_ of the poison should be ascertained and stated. This specially applies to substances that _may_ have been administered medicinally. “If poison be administered _with intent to murder_, it is not necessary that there should be enough in the article administered to cause death, or that it should be given in such a way as to act fatally. If any poison be there, and the intent be proved, the crime of attempting to administer poison is complete.” [Judge’s ruling in _Hartley_, Cent. Crim. Court, May 12th, 1850; _Reg._ v. _Bacon_, Lincoln Summer Assizes, 1857; _Reg._ v. _Southgate_, Chelmsford Lent Assizes; _Reg._ v. _Cluderay_, York, 1849]. For minute directions as to the conduct of toxicological investigations, see Taylor’s Medical Jurisprudence, 1873, I., 202-209; also Guy and Ferrier’s Forensic Medicine, 1881, p. 359, _et seq._ CHAPTER II. TRIALS FOR POISONING BY HYDROCYANIC OR PRUSSIC ACID. Two cases are reported under this head. The first that of John Tawell, for the murder of his mistress, Sarah Hart, at Salthill, near Windsor, tried at the Spring Assizes at Aylesbury, 1845, before the late Baron Parke (Lord Wensleydale). The second—a case of misadventure—the trial of George Ball, a surgeon, at Lewes, for the murder of his mother by the negligent administration of an overdose of this poison, medicinally, before the Lord Chief Justice of the Common Pleas (Coleridge) Summer Assizes, Lewes, 1860. TRIAL OF JOHN TAWELL FOR POISONING SARAH HART AT SALTHILL BY PRUSSIC ACID. _March 12, 13, and 14_, 1845, SPRING ASSIZES, AYLESBURY, _before_ BARON PARKE. HISTORY OF THE CASE. The trial of John Tawell, of Berkhampstead, Berks, for the murder of Sarah Hart, at Hall Place, Slough, attracted more than usual attention, from the cruelty of the act in poisoning the woman whom he had seduced, the position and popular character of the murderer as a benevolent and hospitable Quaker, noted for his charities, and the novelty of the mode by which his detection was mainly insured. The electric telegraph had only very lately been established on the line of the Great Western Railway, and though Tawell lost no time after committing the act, in getting into the train for London at Slough, the telegraph outstripped him, and on his arrival at the Paddington station he was recognised, and tracked to his lodgings, and thus his immediate arrest secured.