Expositions, as we have before remarked, come into the same worshipful guild by right of a special literature they have brought into being.  They come, moreover, into the blue-book range by their bearing upon certain topics generally assigned to it.  It is found, for example, that, like other great gatherings, they are apt to be followed by a temporary local increase of crime.  The police-records of London show that the arrests in 1851 outnumbered those of the previous year by 1570, and that in 1862 the aggregate exceeded by 5043 that of 1861.  It will at once occur that the population of the city was greatly increased on each occasion, and that the influx of thieves and lawbreakers generally must have thinned out that class elsewhere, and in that way very probably reduced, rather than added to, the sum-total of crime, the preventive arrangements in London having been exceptionally thorough.  The drawback that would consist in an increase of crime is therefore only an apparent result.  An opposite effect cannot but result, if only from the evidence that so vast and heterogeneous an assemblage can be held without marked disorder.  The police as well as the criminals and the savants of all nations come together, compare notes and enjoy a common improvement.

[Illustration:  THE MAMMOTH RODMAN GUN.]

This is the first opportunity the physicians of Europe have had to become fully acquainted with the advances in surgery and pathology their American brethren have the credit of having made within the past few years.  They will find it illustrated in the government buildings and elsewhere; and they have an ample quid pro quo to offer from their own researches.  The balancing of opinions at the proposed medical congress and in private intercourse must tend to free medical science from what remnants of empiricism still disfigure it, to perfect diagnosis and to trace with precision the operation of all remedial agents.  Means remain to be found of administering the coup de grace to the few epidemics which have not yet been extirpated, but linger in a crippled condition.  This will be aided by the illustrations afforded of processes of draining, ventilation, etc.

Man’s health rests in that of his stomach.  The food question is a concern of the physician as well as of the publicist.  The race began life on a vegetable diet, and to that it reverts when compelled by enfeebled digestion or by the increasing difficulty of providing animal food for a dense population.  But it likes flesh when able to assimilate it or to procure it, and demands at least the compromise of fish.  Hence, the revived attention to fish-breeding, an art wellnigh forgotten since the Reformation emptied the carp-ponds of the monks.  Maryland, New York and other States illustrate this device for enhancing the food-supply, and the aquaria at Agricultural Hall, containing twelve or fifteen thousand gallons of salt and fresh water, present a congress of the leaders,