In 1850, a Select Committee of the House of Commons, presided over by Sir George Grey, the then Home Secretary, expressed the opinion that, under proper regulation and control, separate confinement is more efficient than any other system which has yet been tried, both in deterring from crime and in promoting reformation, but that it should not be enforced for a longer period than twelve months; and that hard labour is not incompatible with individual separation. The student of the English Prison System must be careful to bear in mind at this juncture that the Secretary of State was not, as he now is, the supreme head of all Prisons in the country. He only had control over prisons where persons sentenced to Transportation might be confined. Pentonville, therefore, was not a local prison to which prisoners of the Metropolis would be committed in the ordinary course, but was specially built in order that an experiment of the System of Separate Confinement might be made by the authority of the Government under the best possible direction and superintendence. The corpus on which this experiment was made were first offenders between eighteen and thirty-five sentenced to Transportation, for whom a period, not to be prolonged beyond eighteen months, should be one of instruction and probation, rather than of severe punishment before the convict was shipped to Van Diemen's Land. Everything was done to render the separation real and complete: exercise was taken in separate yards, and masks were worn to prevent recognition. While primarily the Pentonville system was applied to convicts only, and became in fact the basis of our penal servitude system, as explained in the former chapter, yet it led indirectly to the establishment of the separate system in Local Prisons throughout the country. Although the Secretary of State had no control over the administration of Local Prisons, yet, apart from the influence which the Secretary of State would naturally exercise in directing public opinion in such a matter, an Act of 1835 had made provision that all Rules framed by local Justices for Prisons should be subject to his approval; and the Act of 1844 authorised the appointment of a Surveyor General of Prisons to aid the Secretary of State by ensuring that due attention was given by local Authorities to the requirements of proper prison construction as prescribed by Act of Parliament. Thus the Separate System became gradually established throughout the country, both for convicts in the early stage of their imprisonment, and for those committed to the County and Borough Gaols, although uniformity was very far from being established owing to the absence of any central control. It was this absence of uniformity which led later, as we shall see, to the complete centralization of the Prison System, which was effected finally by the Prison Act, 1877.