A Short Bright Flash: Augustin Fresnel and the Birth of the Modern Lighthouse 1st Edition

I bought the Kindle version but wished I had the hard copy to better see the interesting illustrations. The story moves right along, keeping the reader's interest and not getting bogged down in the science. The book is organized into seven sections plus a preface and introduction. The preface describes the author's childhood interest in the Fresnel lens. The introduction describes one of the deadly shipwrecks of the early 1800's that were the impetus for building lighthouses. As the title of the book indicates, "a short bright flash" that can be seen far away is needed. Since the Earth's surface is curved, the light must be high enough off the ground to be seen at a distance. Using geometry, an object 100 feet above sea level is visible 12 miles away at sea level. However, the intensity of the light must be strong enough to be seen. This is done by using a concentrating lens and rotating the light so all points on the horizon are covered. The problem is that a conventional glass lens of several feet diameter becomes very thick and thus too heavy to be hoisted 100-ft into the air. The Fresnel lens is broken into small segments and is much flatter and lighter weight.The book describes Fresnel's life and the Fresnel lens in seven parts:(1) "Dreams of glory" describes his early life and the winning of an award for the analysis of diffraction.(2) "The flash of brilliance" describes his development of an improved lighthouse lens(3) "The dream of total refraction" gives examples of sizes (up to 6-ft diameter lens) and locations of lighthouses.(4) "Race to perfection" describes the challenges to the glass industry to make precision 6-foot lens(5) "The American exception" tells of the deployment of lighthouses in America(6) "Everything recklessly broken" refers to the American Civil War's impact on lighthouses(7) "The golden age" describes the building of lighthouses around the world.There are also extensive Notes and an Index.This is altogether a very enjoyable and well written book.

This book can be divided into two parts, roughly of equal length. The first part of the book is a biography of the French civil engineer Augustin Fresnel that emphasizes his contributions to optics, particularly his development of the "Fresnel lens." This part of the book also describes the political and technological complications that accompanied the adoption of this lens for lighthouses throughout Europe (mainly France and Britain). The second part of the book concerns lighthouses in the United States. It is mainly the story of how the very poor system of lighthouses in the U.S. was finally updated to equal European systems just before the American Civil War. It describes how politics, cronyism, and the lack of technical expertise had to be overcome to accomplish that feat.The book is easy to read and only starts to "drag" in the second part, when the details of who (politician, engineer, etc.) visited which lighthouse for what purpose becomes a bit monotonous.Fresnel's accomplishments in optics are legendary, and I was disappointed that the author (an MIT physics graduate) didn't provide the reader with a little more insight into the physics behind his ideas. This is my reason for giving the book only three stars. Below I describe a few places where the technical presentation could have been better.The figure on page 31 is for one of Fresnel's constructions used to explain diffraction. It is said to be for "two waves coming through parallel double slits," but I believe it is really for a wave incident on an opaque obstacle (the line A-B). It shows how diffraction causes light to enter the shadow region behind the obstacle producing diffraction bands (light and dark stripes). The author missed an opportunity to explain to the reader how Fresnel's simple construction predicted this phenomenon, which was a remarkable accomplishment at the time. The figure is also poorly reproduced – it is too small to show some of the details.On page 56, we have the statement "Even the most flawless mirror lost half its light on reflection (half is absorbed, half is reflected)," and on page 79 "Unlike mirrors, which lost half of their light at the point of reflection, this prism would lose nothing at all." These statements might lead the reader to believe that there is something inherent about a mirror that makes one lose half of the light (energy), but this is not the case. A modern mirror made from aluminum can lose less than 10% of the light due to absorption on reflection. It was the poor quality of the metal mirrors used for the early light houses that led to the 50% loss of light.The caption for the figure on page 57 says "Several biconvex lenses (one is shown in profile to the right) were installed..." The profile is not for a biconvex lens, but it is for a plano-convex lens.The figures are not numbered, and the captions are often brief. There are also no credits for the figures, so one has no idea if a figure is an original due to Fresnel, Arago, ... or simply an artist rendition.The book (hardcover) is very well produced – printed in Canada. The typeface is pleasing, the paper is of good quality, and the signatures are sewn-in.

An interesting combination of technical history and application. Augustin Fresnel, a French engineer active in the early nineteenth century, came up with the idea of using prisms to concentrate light from a flame to make brighter lighthouse lights. He may not have been the first to think of this (although he didn't seem to know of any precedents until other people mentioned them after he expressed the idea) but he brought it into practice. Apparently using a mirror to reflect light causes half of the light to be lost (how?) while using a prism to focus the light does not; and a series of concentric prisms was much lighter than an entire lens would be. As most ships were lost on various navigational hazards near the coast, rather than in the open ocean, lighthouses that could alert mariners to the location of these hazards were useful infrastructure. Despite difficulties in casting the glass in the unusual shapes needed, fresnel lenses were used first in France, and then spreading to Britain and other countries. The United States took some time to get on board, only making a serious effort in the 1850s after some ill-advised penny-pinching was overcome after years of effort. Lighthouses were important features to capture or destroy in the American Civil War; the Union naval forces, being unfamiliar with the southern coasts they wished to blockade. especially benefited form maintaining or re-establishing lighthouses with fresnel lenses, while the Confederate forces often tried to destroy lighthouses likely to be helpful to the Union. Although lighthouses equipped with fresnel lenses continued to spread after the 1860s, the technology doesn't seem to have changed very much. The development of various radio and radar navigational aids during the Second World War, and now GPS, have reduced the importance of lighthouses.

The story of Fresnel's lens systems, their installation in lighthouses around the world & their part in developing our global civilisation is brilliantly (!) told. The US episodes are particularly fascinating, & given their due weight here.I need my history to be thorough, & Theresa Levitt reveals how light & Enlightenment have been linked, through the lighthouse age & into the present. Very interesting & enjoyable for anyone!

This book is immediately disappointing in that it includes only 2 photographs of Lighthouse Lenses, when surely a book about the Inventor of the Fresnel system should be replete with examples of the variety and diversity of lenses that his genius enabled to be constructed. Though the text (presently unread) is illustrated with scale drawings, engraved pictures and the like, many of which are small and appear to be somewhat peripheral to the subject, the lack of photos of actual lenses is a great let down.

A very interesting book on the early days of lighthouses. A worth while read for anyone who is interested in early lighthouse technology.

For anyone that is interested in the working history of the light house. This book covers the subject matter without getting stuck in the technical aspects of the story. A good all around read.