Today is the birthday of Robert Hooke, arguably the greatest experimental scientist of the 17th century. Unfortunately no portrait survives, and the image here is merely an attempt by a modern artist to give us some idea, although I have no idea what information the facial features are based on. Hooke’s relative obscurity is due in large part because his contemporaries, notably Sir Isaac Newton, sought to downplay his role in key areas of scientific discovery. Hooke’s interests were vast. He made contributions in fields such as physics and astronomy, chemistry, biology, geology, architecture and naval technology. He collaborated or corresponded with scientists as diverse as Christian Huygens, Antony van Leeuwenhoek, Christopher Wren, Robert Boyle, and Isaac Newton. Among other accomplishments, he invented the universal joint, the iris diaphragm, and an early prototype of the respirator; invented the anchor escapement and the balance spring, which made more accurate clocks possible; served as Chief Surveyor and helped rebuild London after the Great Fire of 1666; worked out the correct theory of combustion; devised an equation describing elasticity that is still used today (“Hooke’s Law”); assisted Robert Boyle in studying the physics of gases; invented or improved meteorological instruments such as the barometer, anemometer, and hygrometer; pioneered microscopy and discovered the cell; and established an accurate understanding of the origins of fossils.
Relatively little is known about Robert Hooke’s life. He was born on July 18, 1635, at Freshwater, on the Isle of Wight, the son of a clergyman. He was educated at home by his father until he died when Hooke was 13. His father left him an inheritance of 40 pounds, intended for Hooke to use to buy an apprenticeship as a watchmaker (because he had shown extraordinary skill at an early age with mechanical things). Although he did travel to London to start an apprenticeship he wound up at Westminster School where he studied the classics and Euclid. Subsequently he entered Oxford as a choir scholar in 1653.
At Oxford he was employed as a “chemical assistant” to Dr Thomas Willis, for whom Hooke developed a great admiration. There he met the natural philosopher Robert Boyle, and gained employment as his assistant from about 1655 to 1662, constructing, operating, and demonstrating Boyle’s “machina Boyleana” or air pump. It is known that Hooke had a particularly keen eye, and was an adept mathematician, neither of which applied to Boyle. It has been suggested that Hooke probably made the observations and may well have developed the mathematics of Boyle’s law (concerning the pressure and volume of gases). Regardless, it is clear that Hooke was a valued assistant to Boyle, and the two retained a mutual high regard. Hooke himself characterized his Oxford days as the foundation of his lifelong passion for science, and the friends he made there were of paramount importance to him throughout his career, particularly Christopher Wren.
It is impossible to examine all of the areas of inquiry in which Hooke excelled and made major contributions. The lead paragraph here will have to suffice. Instead I will focus on two subjects simply because they are of professional interest to me: microscopy and paleontology.
Hooke’s reputation in the history of biology largely rests on his book Micrographia, published in 1665. Hooke devised the compound microscope and illumination system and with it he observed organisms as diverse as insects, sponges, bryozoans, foraminifera, and bird feathers. Micrographia was an accurate and detailed record of his observations, illustrated with magnificent drawings, such as the flea (pictured), which Hooke described as “adorn’d with a curiously polish’d suite of sable Armour, neatly jointed. . .” It was a best-seller of its day.
Perhaps his most famous microscopical observation was his study of thin slices of cork, (pictured). In “Observation XVIII” of the Micrographia, he wrote:
I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this. . .
Hooke had discovered plant cells — more precisely, what Hooke saw were the cell walls in cork tissue. In fact, it was Hooke who coined the term “cells”: the boxlike cells of cork reminded him of the cells of a monastery.
Hooke was also a keen observer of fossils and geology. While some fossils closely resemble living animals or plants, others do not — because of their mode of preservation, because they are extinct, or because they represent living taxa which are undiscovered or poorly known. In the seventeenth century, a number of hypotheses had been proposed for the origin of fossils. One widely accepted theory, going back to Aristotle, stated that fossils were formed and grew within the Earth. A shaping force, or “extraordinary Plastick virtue,” could thus create stones that looked like living beings but were not.
Hooke examined fossils with a microscope — the first person to do so — and noted close similarities between the structures of petrified wood and fossil shells on the one hand, and living wood and living mollusc shells on the other. In Micrographia he compared a piece of petrified wood with a piece of rotten oak wood, and concluded that,
“this petrify’d Wood having lain in some place where it was well soak’d with petrifying water (that is, such water as is well impregnated with stony and earthy particles) did by degrees separate abundance of stony particles from the permeating water, which stony particles, being by means of the fluid vehicle convey’d, not onely into the Microscopical pores. . . but also into the pores or Interstitia. . . of that part of the Wood, which through the Microscope, appears most solid.”
He is spot on: dead wood can be turned to stone over time by the action of water rich in dissolved minerals, depositing those minerals throughout the wood. Hooke also concluded in Micrographia that the shell-like fossils that he examined really were,
“the Shells of certain Shel-fishes, which, either by some Deluge, Inundation, earthquake, or some such other means, came to be thrown to that place, and there to be fill’d with some kind of Mud or Clay, or petrifying Water, or some other substance. . . ”
Hooke had grasped the cardinal principle of paleontology — that fossils are not “sports of Nature,” but remains of once-living organisms that can be used to help us understand the history of life. Hooke realized, two and a half centuries before Darwin, that the fossil record documents changes among the organisms on the planet, and that species have both appeared and gone extinct throughout the history of life on Earth.
Hooke gained a reputation (undeserved) of being anti-social, mostly gained from the fact that he spent so much time defending his scientific prowess against contemporaries, and thereby appearing to be an irascible misanthrope. He was anything but. There is ample documentation of him enjoying evenings in the tavern or dining with Boyle. One great tavern food is the meat pie, still very much in evidence in pubs at lunch time when I was at Oxford. Here’s a pie recipe taken from The Closet of the Eminently Learned Sir Kenelme Digbie Kt. Opened, first printed in 1669. This is a 17th-century English cookbook and a resource of the types of food that were eaten by persons of means in the 17th century in England. It is supposedly based upon the writings of Sir Kenelm Digby, a privateer whose interests included cooking, medicine, swordplay, astrology, alchemy, literature, and natural philosophy.
First, here is the original:
My Lady Of Portland’s Minced Pyes
Take four pounds of Beef, Veal or Neats-Tongues, and eight pounds of Suet; and mince both the meat and Suet very small, befor you put them together. Then mingle them well together and mince it very small, and put to it six pounds of Currants washed and picked very clean. Then take the Peel of two Limons, and half a score of Pippins, and mince them very small. Then take above an Ounce of Nutmegs, and a quarter of an Ounce of Mace, some Cloves and Cinnamon, and put them together, and sweeten them with Rose-water and Sugar. And when you are ready to put them into your Paste, take Citron and Orangiadoe, and slice them very thin, and lay them upon the meat. If you please, put dates upon the top of them. And put amongst the meat an Ounce of Caraway seeds. Be sure you have very fine Paste.
My Lady of Portland told me since, that she finds Neats-tongues to be the best flesh for Pies. Parboil them first. For the proportion of the Ingredients she likes best to take equal parts of flesh, of suet, of currants and of Raisins of the Sun. The other things in proportion as is said above. You may either put the Raisins in whole, or stone the greatest part, and Mince them with the Meat. Keep some whole ones, to lay a bed of them at the top of the Pye, when all is in. You will do well to stick the Candid Orange-peel, and green Citron-peel into the meat. You may put a little Sack or Greek Muscadine into each Pye. A little Amber-sugar doth well here. A pound of flesh, and proportionably of all things else, is enough for once in a large family.
I have a hard job getting my mind around a recipe that begins with 12 lbs of meat and fat, but thankfully Sir Kenelme helps us out by saying that 1 lb of meat (plus 1 lb of fat) will serve an average family, so we can begin reconstruction on that basis. You might also balk at a pie made with tongue. If so I believe that veal breast would make an acceptable substitute. The reason I chose this recipe is that it is akin to meat pie recipes that were popular well into the late 19th century. This kind of meat pie heavy with fruit and spices is, of course, the original version of the mincemeat pie. The “meat” in “mincemeat” really was meat until 100 years ago. There is not as much sugar in this recipe as there would be in a sweeter dessert pie, though. The thing that makes this pie a little unusual is the top layer of candied citron, candied orange, and dates. It is always best if you can make the candied peel yourself, especially in this case where you need whole slices (if possible). I have not actually made this specific recipe but I have experimented a great deal with similar ones. So here’s my interpretation.
My Lady Of Portland’s Minced Pyes
½ lb beef tongue of veal breast
½ lb ground suet
¼ lb currant
¼ lb golden raisins
1 cooking apple cored, and diced fine
½ tsp nutmeg
½ tsp powdered mace
½ tsp powdered cloves
½ tsp cinnamon
1 tsp caraway seeds
2 tbsps brown sugar
1 tbsp rosewater
zest of 1 lemon grated
candied citron and orange
dates, pitted and halved lengthwise
1 egg, beaten
Preheat oven to 425°F
In a large mixing bowl thoroughly mix the meat, suet, currants, raisins, apples, sugar, spices, lemon zest, rosewater, and a pinch of salt. Grease a 9” pie dish and line with pastry.
Place the meat filling into the dish. Top with a single layer of candied fruits. Then top with pitted dates .
Cover with the second circle of pastry and flute the edges. Cut slits in the top crust to allow steam to escape. Brush the pastry with egg.
Bake 40 to 50 minutes or until the crust is lightly browned.
Can be served hot or cold.
As a small after note in tribute to Hooke’s work with the microscope here’s an image of the sugar in this recipe under an electron microscope.