"Whoever at the seaside has not had a microscope and an aquarium has yet to learn what the highest pleasures of the seaside are." So said Herbert Spencer, an eminent British intellectual, in 1860. And he was not alone. In the United States, the Ladies' Repository announced that health, recreation, and information "combine in making a Summer holiday at the sea-side one of the most delightful passages of every-day life," adding that a microscope at the sea-side affords "rare revelations of the wisdom and skill of the Creator." While any microscope might do, some were designed specifically for this purpose. These tended to be simple, inexpensive, and small enough to fit in one's pocket.
Sea-side microscopy was a subset of nature study, a hobby for the well-to-do that became widespread in the 19th century. As scientific observations and ideas proliferated, popularizers began presenting sophisticated information in terms suitable for non-specialists. As new paper and printing technologies came on board, books and magazines became less expensive and more numerous. And as the middle class expanded and public transit access increased, more people had the leisure needed to learn about and appreciate the wonders of the universe. Thus, J. E. Taylor could say, in Half-Hours at the Sea-Side (London, 1872), that the sea-side visit was "now almost an annual occurrence to most people," and that microscopes make these visits "more interesting and instructive."
The microscope, the key instrument of nature study, was invented around 1600. By the late 1700s, it had become sufficiently powerful and user-friendly that, in the words of the Encyclopaedia Britannica, "among all the inventions that ever appeared in the world, none, perhaps, can be found so constantly capable of entertaining, improving, and satisfying the mind of man."
A writer in the 1850s noted that "we appear to be on the eve of a microscope mania." In some instances, the microscope was "an indispensable aid to science." And in many instances it offered "an inexhaustible treasury of amusement to crowds of amateurs who aim no higher than to obtain a little useful information respecting the nature of the ordinary objects by which they are surrounded, and are content to admire beauty and variety of design, even when they cannot penetrate to final causes."