Hooke's Micrographia

We're here at the Harvard University Botany Library looking at a first edition of Robert Hooke's Micrographia, published in 1665. This is the first book to show the microscopic structure of materials, and it has a number of remarkable drawings in it. Here we see drawings of silk. These are two different silks. On the top here, we have a fine-waled silk. And in this more detailed drawing down here, you can see the pattern of the weaving of the silk. The bottom image here is a drawing of watered silk. And over here, there's another higher magnification image. And you can see the pattern here is more sharply angled, and it appears that this sharper angle here gives the different texture to the surface finish of the silk. So here we see a drawing of charred wood, and one of the things I find interesting about this drawing is how similar it is to modern electron micrographs that you see of wood. And in this drawing, we can see two of the main features. We see these small cells, which are fibers, which provide structural support to the tree. And we see these larger cells here, which are vessels, which allow fluids to go up and down the tree. And here we see a drawing of the surface of a rosemary leaf with its unexpected tiny little barbs. And this is something that you can only see with a microscope. You wouldn't expect to see those when you just feel the surface of a rosemary leaf. So it's kind of interesting that with the microscope, you can see these features that are invisible to the naked eye. One of the main themes of material science is that the properties of materials are related to their structure. And so being able to see the structure at a microscopic scale is very helpful. And today, we can even see the structure at the atomic scale. Robert Hooke understood this idea. And in the description of the court, Hooke states, I no sooner discerned these, which were the first microscopical pores I ever saw, but me thought that I had, with the discovery of them, perfectly hinted to me the true and intelligible reason for all of the phenomena of quark. So what he's saying here is that by looking at the structure and looking at these cells here in the drawing, he thinks he can understand the properties of quark or the phenomena of quark. What was it about Robert Hooke that allowed him to make this book? Why was it him and not somebody else? Well, Robert Hooke had kind of an interesting history. He grew up on the Isle of Wight, and as a boy, he loved making drawings, and he got quite skilled at making drawings. The other thing was he loved making models of things. He made models of ships. He made a wooden clock that was a working clock when he was a kid. And as a teenager, he moved to London, and he became an apprentice to Sir Peter Lilly, who was a famous painter of the time. So his drawing was good enough that he would be working with a very well-known painter. After he did that, he went to the Westminster School, and he studied classics. He studied mathematics, but he also learned to use a lathe, and this was also very helpful in him making various sorts of apparatus. And as a student at Oxford, he worked in the lab of Robert Boyle, and his job in that lab was to develop scientific apparatus, and he did things like he built pumps that allowed Robert Boyle to do the experiments that led to Boyle's Law. When he returned to London after Oxford, he became the curator of experiments at the Royal Society, and one of the things he did was he got a microscope. He improved that microscope, increasing their magnification, which was what allowed him to make the beautiful drawings that we see today. And here in the preface of the book, we see that he even made a drawing of his microscope. So this thing down here, this is Robert Hooke's microscope. The development of new microscopes with higher and higher magnifications continues to this day. Scanning electron microscopes were invented in the 1960s, and today we have transmission electron microscopes and atomic force microscopes with even higher magnifications. At these higher magnifications, we can see details that Hooke was unable to see because of the limitations of the microscope that he had, the optical microscope. But it's interesting to see today the images we see in a scanning electron microscope at a similar magnification to those that Hooke saw in his optical microscope. And it's remarkable to see how many of the features that we see in these much more fancy microscopes that he was able to capture in his drawings with his simple optical microscope. Okay, so here we have a picture of cork. We have Hooke's drawings showing two perpendicular planes. We also have this nice little drawing of a cork branch here. Cork is the bark from the cork oak tree. And in Hooke's drawings of the microstructure, we can see these cells here are roughly box-like. They're more or less rectangular. And these cells here look more or less circular. So there's these two different perpendicular planes in the cork. And when we look at these scanning electron micrographs, we can see a very similar structure. There's some cells that are roughly box-like and others that are more or less hexagonal or roughly rounded. One feature that Hooke was not able to see, though, that you do see on the scanning electron micrographs is the waviness in the cell walls. And that was because the resolution of his microscope was insufficient to see that level of detail. And here in this illustration, on the bottom here is a drawing of sponge. And when we look at the scanning electron micrograph, we see that the structure is remarkably similar to what Hooke has drawn. So here we have Hooke's drawing of feathers. And we can see he's made several drawings at different length scales. And if we look at this one here, we see the barbule. And you can see there's little hooked regions there. And those hooks lock in to the little feathers over on this side over here of the adjacent barbule. And in the higher magnification picture, you can see on one barbule, there's hooks on one side, but not on the other. And it's this hooking of the two sections together that allows the feathers to maintain a smooth surface for the wing when the bird is flying. And you can see the same sort of thing when you look at the electron micrographs. You can see the little hooks on one side of the barbules, and you can see how they interconnect together with the next barb. One of the most reproduced images from Hooke's book is that of the flea, this image we see here. And you can see why, it's a gorgeous image. And it shows details that people had never seen before. People were amazed to see that the little flea that they might've found on their dog or something was actually made up of this compound body with all these little plates and little hairs here. And you can see these little tiny claws on the legs, and the legs have all these hairs. Nobody had any idea that this is what a flea actually looked like. And so it was an amazing drawing, and it was something that people were just stunned by when Hooke's book came out. And if we look at a modern electron micrograph, we can see it's remarkably similar if we look at the same magnification. So Hooke showed many of the same details, showed some of the same hairs on the legs, showed the same sorts of plates, showed the claws at the ends of the legs. And our modern image is probably from a different species of flea. We don't know what species of flea that Hooke actually looked at, but you can see there's a tremendous similarity between the two images. And it's remarkable how many of the features that Hooke was able to capture in his drawing. And here we have the compound eye of the fly. And this again was astonishing to people in Hooke's day. And even today, people look at this image and they're pretty amazed at the detail in this drawing. And again, we can compare this with a modern electron micrograph. And again, you can see the similarities between what Hooke saw and what we see in a modern scanning electron microscope at a similar magnification. In the 1980s, atomic force microscopes were invented, which have a resolution down to tens of nanometers. And today there's transmission electron microscopes, which allow you to see the atomic structure. So for instance, in a crystal lattice, you can see the individual atoms and the regular crystal structure. Today, most experimental studies of materials include photographs of the microscopic structure of the material taken through some sort of microscope. And the remarkable thing is that all of these studies really trace back to this book here that we're looking at today, to Robert Hooke's Micrographia.