Notes: 

1.  The author of these pages, with one of his friends, was recently induced to visit this most interesting establishment, after midnight, during the progress of a very important debate.  The place was illuminated with gas, and was light as the day:  there was neither noise nor bustle; and the visitors were received with such calm and polite attention, that they did not, until afterwards, become sensible of the inconvenience which such intruders, at a moment of the greatest pressure, must occasion, nor reflect tha the tranquility which they admired, was the result of intense and regulated occupation.  But the effect of such checks in the current of business will appear on recollecting that, as four thousand newspapers are printed off on one side within the hour, every minute is attended with a loss of sixty-six impressions.  The quarter of an hour, therefore, which the stranger may think it not unreasonable to claim for the gratification of his curiosity (and to him this time is but a moment), may cause a failure in the delivery of a thousand copies, and disappoint a proportionate number of expectant readers, in some of our distant towns, to which the morning papers are dispatched by the earliest and most rapid conveyances of each day.

This note is inserted with the further and more general purpose of calling the attention of those, especially foreigners, who are desirous of inspecting our larger manufactories, to the chief cause of the difficulty which frequently attends their introduction.  When the establishment is very extensive, and its departments skilfully arranged, the exclusion of visitors arises, not from any illiberal jealousy, nor, generally, from any desire of concealment, which would, in most cases, be absurd, but from the substantial inconvenience and loss of time, throughout an entire series of well-combined operations, which must be occasioned even by short and causual interruptions.

2.  It is true that the transport of letters is not the only object which this apparatus answers; but the transport of passengers, which is a secondary object, does in fact put a limit to the velocity of that of the letters, which is the primary one.

3.  A proposal for such a vessel, and description of its construction, by the author of this volume, may be found in the Encyclopaedia Metropolitana, Art.  Diving Bell.

4.  The mines of Bolanos in Mexico are supplied with timber from the adjacent mountains by a slide similar to that of Alpnach.  It was constructed by M. Floresi, a gentleman well acquainted with Switzerland.

Chapter 29

On the Duration of Machinery

340.  The time during which a machine will continue to perform its work effectually, will depend chiefly upon the perfection with which it was originally constructed upon the care taken to keep it in proper repair, particularly to correct every shake or looseness in the axes—­and upon the smallness of the mass and of the velocity of its moving parts.  Everything approaching to a blow, all sudden change of direction, is injurious.  Engines for producing power, such as windmills, water-mills, and steam-engines, usually last a long time.(1*)