Population, Leeuwenhoek and National Geographic

National Geographic is running a special series on population – and who is leading the way on population estimates?

Though his tiny peephole gave him privileged access to a never-before-seen microscopic universe, he spent an enormous amount of time looking at spermatozoa, as they’re now called. Oddly enough, it was the milt he squeezed from a cod one day that inspired him to estimate, almost casually, just how many people might live on Earth. Nobody then really had any idea; there were few censuses. Leeuwenhoek started with an estimate that around a million people lived in Holland. Using maps and a little spherical geometry, he calculated that the inhabited land area of the planet was 13,385 times as large as Holland. It was hard to imagine the whole planet being as densely peopled as Holland, which seemed crowded even then. Thus, Leeuwenhoek concluded triumphantly, there couldn’t be more than 13.385 billion people on Earth—a small number indeed compared with the 150 billion sperm cells of a single codfish!

Not very accurate, but he was the first to consider our planet’s population.

Read 7 Billion for more on Leeuwenhoek and population at National Geographic.

The Lens is on Leeuwenhoek

Douglas Anderson at Lens on Leeuwenhoek, the web’s premier English site for all things Leeuwenhoek-ish, has developed a new video called The Life, Times,  and Accomplishments of Antony van Leeuwenhoek 1632 – 1723.

The bad news is that it is only 7 min. 41 seconds long.

The good new is that more videos are in production, and we seem to entering a new era of Leeuwenhoek interest. From the YouTube introduction to the video:

This video is an overview of the life, times, and accomplishments of Antony van Leeuwenhoek (1632-1723), the Dutch scientist who used hand-made single-lens microscopes to become the first human to see protozoa, bacteria, sperm, and red blood cells, among many other things.

Now, the YouTube video is good, but higher quality videos are available for downloading at the Lens on Leeuwenhoek website.

Gazing into my crystal ball (O.K, it’s an old up-turned goldfish bowl and an email from Mr Anderson…) I forsee great things coming from Lens on Leeuwenhoek ….perhaps some new translations of Leeuwenhoek letters? Videos on The Golden Age? I am looking forward to what is to come, and I greatly appreciate the work that Douglas Anderson is doing  to keep the name of Leeuwenhoek alive and prospering.

Leeuwenhoek’s Legacy to the Royal Society III

Continuing, the construction of the microscope and specimen mounting techniques are described:

It were endless to enter into any Particulars, of what is to be observed in any of these Objects, or indeed to give any Account of Mr. Leeuwenhoek’s Discoveries ; they are so numerous as to make up a considerable Part of the Philosophical Transactions, and when collected together, to fill four pretty large Volumes in Quarto, which have been publish’d by him at several Times : And of such Consequence, as to have opened entirely new Scenes in some Parts of Natura! Philosophy, as we are all sensible, in that famous Discovery of the Animálculo, in Semine Masculino, which has given a perfectly new Turn to the Theory of Generation, in almost all the Authors that have since wrote upon that Subject.

leeuwenhoek_microscope.jpgFor the Construction of these Instruments, it is the fame in them all, and the Apparatus is very simple and convenient : They are all single Microscopes, consisting each of a very small double Convex-Glass, let into a Socket, between two Silver Plates rivetted together, and pierc’d with a small Hole : The Object is placed on a Silver Point, or Needle, which, by Means of Screws of the same Metal, provided for that Purpose, may be turn’d about, rais’d, or depress’d, and brought nearer, or put farther from the Glass, as the Eye of the Observer, the Nature of the Object, and the convenient Examination of its several Parts may require.

Mr. Leeuwenhoek fix’d his Objects, if they were solid, to this Silver Point, with Glew -, and when they were Fluid, or of such a Nature as not to be commodiously view’d unless spread upon Glass, he first fitted them on a little Plate of Talk, or excessively thin-blown Glass, which he afterwards glewed to the Needle, in the fame Manner as his other Objects. The Observation, indeed, of the Circulation of the Blood, and some others, require a somewhat different Apparatus, and such a one he had, to which he occasionally fix’d these same Microscopes ; but as it makes no Part of this Cabinet, I shall omit giving any farther Account of it, only taking Notice that it may be seen in a Letter to the Royal Society, of the 12th of January, 1689, and printed in his Arcana Natures Detecta, №. 69. But I was willing to mention just so much, as it may serve to shew the universal Use of these Microscopes, and as it induces me (among other Things) to believe, these were the Kind of Microscopes generally, if not solely, üs’d by this curious Gentleman in all his Observations, and to which we are oblig’d for his most surprizing Discoveries.