让-巴蒂斯特·毕奥Jean-Baptiste Biot

让-巴蒂斯特·毕奥的父亲是Joseph Biot，其祖先曾是洛林的农民，后在财政部担任重要职务。毕奥在巴黎的路易大帝学院接受教育，专攻古典学。他于1791年在路易大帝学院完成学业，此后，由于父亲希望他从事商业，他便跟随路易·安托万-勒内·莫迪学习数学，后者是法兰西公学院的数学教授。Joseph Biot随后将儿子送到勒阿弗尔，给一位商人当文书助理。他的工作包括抄写大量信件（我们得感谢复印机！），这让毕奥感到非常无聊，于是他自愿参军。他于1792年9月加入法国军队，并在1793年9月的翁德肖特战役中服役于炮兵部队。在这场战役中，法国击败了围攻敦刻尔克的英国和汉诺威士兵。战役后，毕奥因患病决定离开军队，回到父母身边。当他步行前往巴黎时，一位乘坐马车的重要人物与他交好。他让毕奥坐上马车前往巴黎，在那里他（毕奥）作为逃兵被捕（他仍穿着军装），并被带到革命委员会面前。如果不是那位陌生人介入，这将对毕奥产生严重后果，他最终获释。尽管毕奥努力寻找，他仍未能确认那位重要陌生人的身份并向他致谢。

毕奥花了几个月从疾病中恢复，在此期间他继续学习数学。他参加了桥梁与道路学校的入学考试，并于1794年1月被录取。巴黎综合理工学院于1794年晚些时候成立（第一年实际上名为“中央公共工程学校”），毕奥于同年11月转学到那里。加斯帕尔·蒙日，巴黎综合理工学院的创始人之一，教授第一批学生，很快意识到了毕奥的潜力。然而，毕奥很快卷入学生政治，并被任命为部门领导。保皇党对国民公会发动了一次未遂起义，毕奥参与其中。他被政府军俘虏并成为囚犯。如果不是加斯帕尔·蒙日，他无法看到拥有如此才华的人留在监狱，甚至死亡，成功恳求释放他，他前途光明的职业生涯可能就此结束。考虑到他生活在法国大革命时期的危险时代，他第二次接近死刑判决并不令人惊讶。他回到巴黎综合理工学院继续学业，与同学西莫恩·德尼·泊松结交，并于1797年毕业。他在西尔维斯特·佛朗索瓦·拉克鲁瓦那里找到了赞助人，后者在帮助毕奥发展职业生涯方面极具影响力。

1797年，他成为博韦瓦兹中央学校的数学教授。即使像毕奥这样有能力的人，从本科生直接成为教授，似乎也令人瞩目。然而，事情对他有利[7]：-

1795年2月25日的一项法律中，国民公会呼吁建立中央学校体系，每个大城市设一所，以取代旧制度下的中学，作为中等教育的场所。新学校的课程实用而现代，包括两年专攻数学、实验物理和化学。这些科目以前从未在高中阶段教授过，因此，合格教师短缺是不可避免的。

毕奥在巴黎综合理工学院学习期间，通过他与Barnabé Brisson的友谊得知了数学教授职位的空缺，Barnabé Brisson是安托万 François Brisson de Beauvais的儿子。通过Barnabé Brisson，毕奥认识了他的妹妹Gabrielle。尽管Gabrielle只有十六岁，他们还是在1797年毕奥在Beauvais就职后不久结婚了。毕奥教Gabrielle数学和物理，以便她能将Ernst Gottfried Fischer的德文文本翻译成法文。是Claude Louis Berthollet请毕奥进行翻译，该译本于1806年以Physique mécanique Ⓣ（力学物理）出版。毕奥的妻子受过良好教育且德语流利，因此她的翻译非常出色。然而，按照当时的惯例，书中记录毕奥本人为译者，而非他的妻子。毕奥和他的妻子有一个儿子Édouard Constant 毕奥，生于1803年。

毕奥主要是通过西尔维斯特·佛朗索瓦·拉克鲁瓦被任命到博韦瓦兹的，西尔维斯特·佛朗索瓦·拉克鲁瓦在他工作的最初几年经常给他建议。然而，他也设法从皮埃尔·西蒙·拉普拉斯那里获得了职业上的支持。事实上，在1799年底，毕奥联系了皮埃尔·西蒙·拉普拉斯，后者曾在巴黎综合理工学院教过他，并提出校对当时在出版商手中的Mécanique céleste Ⓣ（《天体力学》）。当皮埃尔·西蒙·拉普拉斯说“不用了，谢谢”时，他并没有放弃，而是以礼貌的方式坚持，最终皮埃尔·西蒙·拉普拉斯同意了。此时，毕奥是巴黎综合理工学院的入学考官，因此经常在巴黎。他写道[7]：-

从那时起，每次我去巴黎，我都会带上我的校对工作，亲自呈交给M 皮埃尔·西蒙·拉普拉斯。他总是和蔼地接收，审阅并讨论，这给了我机会向他提出那些阻碍我的难题。他解释这些问题的意愿是无限的。但即使是他，也不能总是不停下来思考很久就做到。这通常发生在他使用了“很容易看出”这一权宜说法的地方。

当然，毕奥所需付出的努力是巨大的。他在1799年末写道[7]：-

我把所有时间都花在这项工作上[校对《天体力学》]，我觉得它在好几个方面都很重要，我希望我成功了。我像魔鬼一样工作以按时完成它，最后一天我连续工作了十八个小时，不吃不喝。终于，谢天谢地，它完成了，我可以自夸说我理解了《天体力学》Ⓣ。如果这是我从中得到的唯一好处，那也已经很多了。

皮埃尔·西蒙·拉普拉斯也对毕奥正在进行的数学研究感兴趣，并在材料以及如何发表方面给了他建议。1800年，他被任命为法兰西公学院的数学物理教授，这一任命主要归功于皮埃尔·西蒙·拉普拉斯的影响。1800年，毕奥当选为研究所第一级的通讯院士，接替1799年12月去世的J.É. 蒙蒂克拉。在这次选举中，皮埃尔·西蒙·拉普拉斯的支持对毕奥再次至关重要。1803年1月，研究所进行了重组，让·巴蒂斯特·约瑟夫·德朗布尔成为终身秘书，在数学部创造了一个空缺。尽管毕奥在1800年之前已经写出了优秀的数学回忆录，但从那时起他就专注于实验物理学。然而，大概是为了提高他在数学部获得一席之地的机会，他就在选举即将举行之前提交了一篇关于等时曲线轴的回忆录。这足以保持他很高的数学声誉，他于1803年4月11日当选。

第一次以科学为目的的气球升空是由毕奥和Joseph-Louis Gay-Lussac于1804年8月24日从艺术与工艺学院的花园进行的。他们达到了4000米的高度，并测量了不同高度大气的磁、电和化学性质。1806年，再次在皮埃尔·西蒙·拉普拉斯的支持下，毕奥被任命为经度局的天文学助理，此外还担任其他职务。同年9月3日，他与弗朗索瓦·阿拉戈出发前往巴利阿里群岛的福门特拉岛，以完成早先在那里开始的关于计算子午线弧长的工作。1808年5月，拿破仑宣布其兄约瑟夫·波拿巴为西班牙统治者，独立战争爆发时，他们仍在进行测量。毕奥和弗朗索瓦·阿拉戈一定显得极其可疑；两个法国人带着精密的测量仪器在西班牙领土上工作。毕奥立即逃回法国。1808年晚些时候，他与Claude-Louis Mathieu一起，开始了一系列对子午线上不同点秒摆长度的测量，特别是在波尔多和敦刻尔克。Mathieu和毕奥都因这项高度精确的工作于1809年获得了Académie des Sciences的奖项，并于1812年因他们的成就再次获得科学院的奖项。1809年，毕奥被任命为理学院的物理天文学教授。他担任这一职位超过五十年。

毕奥研究了广泛的数学主题，主要是在应用数学方面。他在应用方面在天文学、弹性、电学和磁学、热学和光学方面取得了进展，而在纯数学方面，他也在几何学方面做了重要工作。他与弗朗索瓦·阿拉戈合作研究气体的折射性质。毕奥与菲利克斯·沙伐一起发现，电流通过导线时产生的磁场强度与距导线的距离成反比。这现在被称为毕奥-菲利克斯·沙伐定律，是现代电磁理论的基础。莫里斯·克莱因在评论[8]时写道：-

毕奥完全依靠实验来确定磁铁与直线电流的相互作用，然后推断出关于电流与磁铁之间力的数学定律。

光是毕奥投入时间最多的主题，他做出了晶体物体旋转偏振定律的重大发现。发现这些定律后，他用它们来分析糖溶液，使用他发明的一种称为偏振计的仪器。由于这项关于通过化学溶液的光的偏振的研究，他于1840年被授予伦敦皇家学会的伦福德奖章。他已于1815年当选为皇家学会的外籍院士。

他的重要著作之一是Mémoire sur la figure de la terre Ⓣ（关于地球形状的论文）（1827年），描述了地球的形状。在他的其他主要著作中，我们提到：Analyse de la mécanique céleste de M Laplace Ⓣ（M 皮埃尔·西蒙·拉普拉斯的天体力学分析）（1801年）；Traité analytique des courbes et des surfaces du second degré Ⓣ（关于二次曲线与曲面的分析论著）（1802年）；Recherches sur l'intégration des équations différentielles partielles et sur les vibrations des surfaces Ⓣ（关于偏微分方程积分与曲面振动的研究）（1803年）；Essai de géométrie analytique appliqué aux courbes et aux surfaces de second ordre Ⓣ（应用于二次曲线与曲面的解析几何论著）（1806年）；Recherches expérimentales et mathématiques sur les mouvements des molécules de la lumière autour de leur centre de gravité Ⓣ（关于光分子绕其重心运动的实验研究与数学）（1814年）；Traité de physique experimentale et mathématique Ⓣ（实验物理与数学论著）（1816年）；Precis de physique Ⓣ（物理学概要）（1817年）；（与弗朗索瓦·阿拉戈合作）Recueil d'observations géodésiques, astronomiques et physiques exécutées en Espagne et Écosse Ⓣ（在西班牙和苏格兰收集的大地测量、天文和物理观测集）（1821年）；Mémoire sur la vraie constitution de l'atmosphère terrestre Ⓣ（关于地球大气的真实构成的论文）（1841年）；Traité élémentaire d'astronomie physique Ⓣ（物理天文学基础论著）（1805年）；Recherches sur plusieurs points de l'astronomie égyptienne Ⓣ（关于埃及天文学若干点的研究）（1823年）；Recherches sur l'ancienne astronomie chinoise Ⓣ（关于古代中国天文学的研究）（1840年）；Études sur l'astronomie indienne et sur l'astronomie chinoise Ⓣ（印度与中国天文学研究）（1862年）；Essai sur l'histoire générale des sciences pendant la Révolution Ⓣ（关于大革命期间科学通史的论著）（1803年）；Discours sur Montaigne Ⓣ（关于蒙田的讲座）（1812年）；Lettres sur l'approvisionnement de Paris et sur le commerce des grains Ⓣ（关于巴黎供给与粮食贸易的信件）（1835年）；Traite d'astronomie physique Ⓣ（物理天文学论著）（1850年）；以及Mélanges scientifiques et littéraires Ⓣ（科学与文学笔记）（1858年）。

他曾两次尝试担任Académie des Sciences的秘书一职，为了提高当选该职位的机会，他撰写了Essai sur l'Histoire Générale des Sciences pendant la Révolution。然而，他在1822年输给了约瑟夫·傅里叶，随后在1830年5月约瑟夫·傅里叶去世时，他再次申请秘书职位，这一次又输给了弗朗索瓦·阿拉戈。弗朗索瓦·阿拉戈与毕奥之间的竞争在1839年再次显现，当时不同的摄影工艺正在竞争[10]：-

弗朗索瓦·阿拉戈和毕奥，法国光学领域的顶尖权威，在过去三十年里一直就光学仪器再现世界的能力存在分歧。摄影成为他们又一个产生分歧的机会，而他们并未回避这一任务。这场辩论超越了优先权归属和功劳分配的问题。其核心在于摄影表面显示了什么，可见的印记与真实世界之间存在何种关系。

弗朗索瓦·阿拉戈支持使用银板的达盖尔摄影工艺，而毕奥则拥护由威廉·亨利·福克斯·塔尔博特开发的用浸泡过银溶液的纸张的方法。这并不是因为他认为这种方法能产生更清晰的照片，而是因为他相信这些图像捕捉到了肉眼不可见的“化学辐射”。我们应当注意，“化学辐射”这一概念在当时被广泛相信。毕奥还认为摄影工艺应当保留给科学用途，而不应供公众使用。毕奥和威廉·亨利·福克斯·塔尔博特之间曾有一段合作时期，两人频繁通信。基本上，摄影工艺成为毕奥用于研究光的又一工具，而光一直是他主要的兴趣所在。

除了对几乎每一个科学分支的兴趣外，毕奥还对该学科的历史感兴趣。他出版了关于这一主题的著作，如：Essai sur l'histoire générale des sciences pendant la Révolution française Ⓣ（关于法国大革命期间科学通史的论著）（1803年）；Notice historique sur la vie et les ouvrages de Newton Ⓣ（关于艾萨克·牛顿生平与著作的历史札记）（1822年）；Recherches sur plusieurs points de l'astronomie égyptienne appliquées aux monuments astronomiques trouvés en Égypte Ⓣ（关于应用于埃及发现的天文纪念碑的埃及天文学若干点的研究）（1823年）；Sur la manière de calculer les positions des étoiles relativement à l'équateur et à l'écliptique pour les époques anciennes Ⓣ（如何计算古代恒星相对于赤道和黄道的位置）（1823年）；Opuscule sur l'Astronomie ancienne des Chinois, des Indous et des Arabes Ⓣ（关于古代中国、印度和阿拉伯天文学的小册子）（1840年）；Mémoire sur le Zodiaque de Denderah Ⓣ（关于丹德拉黄道带的论文）（1844年）；Précis de l'histoire de l'Astronomie planétaire Ⓣ（行星天文学史概要）（1847年）；以及Études sur l'astronomie indienne et l'astronomie chinoise Ⓣ（印度天文学与中国天文学研究）（1862年）。

在[4]中，圣伯夫说毕奥最高程度地具备所有好奇心、精细、洞察、精确、巧妙分析、方法、清晰等品质，简言之，具备所有主要和次要品质，只差一个，天才，即原创性和发明意义上的天才。

Olinthus Gregory在1821年的一段形成对比的评论是：-

关于M 毕奥，当我们在泽特兰[=设得兰]群岛共处时，我有机会相当充分地了解他的性格；我毫不犹豫地说，我从未见过像他的性格中所展现的那样，由虚荣、冲动、反复无常和天生的偏袒构成的奇特混合体。

除了我们上面提到的荣誉之外，毕奥还于1814年被授予荣誉军团骑士勋章，并于1849年被授予指挥官勋章。他于1841年当选为铭文与美文科学院院士，并于1856年当选为法兰西学院院士。

Jean-Baptiste Biot's father was Joseph Biot, whose ancestors were farmers in Lorraine, had achieved an important role working in the Treasury. Jean-Baptiste was educated at the college of Louis-le-Grand in Paris, where he specialised in classics. He completed his studies at Louis-le-Grand in 1791 following which, since his father wanted him to make a career in commerce, he took private lessons in mathematics from Antoine-Rene Mauduit who was professor of mathematics at the Collège de France. Joseph Biot then sent his son to Le Havre to become a clerical assistant to a merchant. His job there consisted of copying vast numbers of letters (we have to be thankful for photocopiers!) which bored Biot so much that he volunteered for the army. He joined the French army in September 1792, and served in the artillery at the Battle of Hondschoote in September 1793. In this battle the French defeated the British and Hanoverian soldiers besieging Dunkirk. After the battle Biot, suffering from an illness, decided to leave the army and return to his parents. As he was walking towards Paris, he was befriended by an important person who passed in his carriage. He took Biot in his carriage to Paris where he (Biot) was arrested as a deserter (he was still in uniform) and brought before a revolutionary committee. This would have had serious consequences for Biot had not the stranger intervened and he was set free. Despite Biot's efforts, he was not able to identify the important stranger and thank him.

It took Biot some months to recover from the illness during which time he continued with his studies of mathematics. He took the entrance examinations for the École des Ponts et Chausées and was accepted in January 1794. The École Polytechnique was founded later in 1794 (actually named 'École centrale des travaux publics' for its first year) and Biot transferred there in November of that year. Gaspard Monge, one of the founders of l'École Polytechnique who taught the first intake of students, quickly realised Biot's potential. Biot, however, quickly became involved in student politics and was made a section leader. There was an attempted insurrection by the royalists against the Convention and Biot took part. He was captured by government forces and taken prisoner. Had it not been for Monge, who could not see someone with such talents remain in jail, or even die, pleading successfully for his release his promising career might have ended. It is not surprising that for a second time he had come close to a death sentence, giving the dangerous times in Revolutionary France through which he lived. He returned to his studies at the École Polytechnique, befriending a fellow student, Siméon-Denis Poisson, and graduated in 1797. He had found a patron in Sylvestre-François Lacroix who was highly influential in helping Biot develop his career.

He became Professor of Mathematics at the École Centrale de l'Oise at Beauvais in 1797. It might seems remarkable that even someone as able as Biot could move from being an undergraduate straight into a professorship. However, things had worked in his favour [7]:-

The Convention, in a law of 25 February 1795 had called for a system of Écoles Centrales, one in each large town, to replace the Collèges of the Ancien Régime as seats of secondary education. The curricula of the new schools was practical and modern and included two years devoted to mathematics, experimental physics and chemistry. These subjects had never been taught before on a high school level, so, inevitably, there was a shortage of qualified teachers.

Biot got to know of the vacant mathematics professorship through his friendship with Barnabé Brisson, the son of Antoine François Brisson de Beauvais, while studying at l'École Polytechnique. Through Barnabé Brisson, Biot had got to know his sister Gabrielle. Although Gabrielle was only sixteen years old, they married in 1797 soon after Biot took up his position at Beauvais. Biot taught Gabrielle mathematics and physics so that she might translate into French a German text by Ernst Gottfried Fischer. It was Claude Louis Berthollet who had asked Biot to make the translation which was published as Physique mécanique Ⓣ in 1806. Biot's wife was well educated and fluent in German, so her translation was excellent. However, in line with the practice of the time, the book records Biot himself as the translator rather than his wife. Biot and his wife had a son Édouard Constant Biot who was born in 1803.

It was largely through Lacroix that Biot had been appointed at Beauvais and Lacroix advised him frequently through the first years that he worked there. However, he also managed to get support in his career from Laplace. In fact in late 1799 Biot approached Laplace, who had taught him at l'École Polytechnique, and offered to proof-read the Mécanique céleste Ⓣ which at that time was with the publisher. He did not give up when Laplace said "No thanks" but persisted in a polite way and eventually Laplace agreed. Biot was, by this time, an entrance examiner at the École Polytechnique so was frequently in Paris. He wrote [7]:-

From that time on, each time I went to Paris I brought my proof-reading work and personally presented it to M Laplace. He always received it with kindness, examined it and discussed it, and that gave me the opportunity to submit to him the difficulties that had stopped me. His willingness to explain them was boundless. But even he could not always do it without stopping to think for a long while. This usually occurred in places where he had used the expedient phrase 'it can easily be seen'.

Certainly the effort required by Biot was enormous. He wrote near the end of 1799 [7]:-

I spent all of my days at this work [proof-reading the 'Mécanique céleste'] which I felt to be important in several respects, and I hope I have succeeded. I worked like a devil to finish it on time, and 1 remained at the task eighteen hours in a row the last day, without eating or drinking. Finally, thank heaven, it is finished, and I can flatter myself that I understand the 'Mecanique celeste' Ⓣ. If this were to be the only benefit I would get from it, it would still be a lot.

Laplace was also interested in the research on mathematics which Biot was undertaking and gave him advice both on the material and on getting it published. In 1800 he was appointed Professor of Mathematical Physics at the Collège de France, an appointment which was due mainly to the influence of Laplace. In 1800 Biot was elected an associate to the First Class of the Institute, replacing Jean Montucla who died in December 1799. Again Laplace's support was important to Biot in this election. In January 1803 the Institut was reorganised and Delambre became perpetual secretary, creating a vacancy in the Mathematics Section. Although Biot had produced excellent mathematics memoirs in the years up to 1800, he had concentrated on experimental physics from that time on. However, presumably to improve his chances of gaining a place in the Mathematics Section, he submitted a memoir on the axes of tautochronous curves just before the election was to take place. It was sufficient to keep his mathematical reputation high and he was elected on 11 April 1803.

The first balloon ascent made for scientific purposes was by Biot and Joseph-Louis Gay-Lussac from the garden of the Conservatoire des Arts on 24 August 1804. They achieved a height of 4000 metres and measured magnetic, electrical, and chemical properties of the atmosphere at various heights. In 1806, again with the support of Laplace, Biot was appointed as an assistant astronomer at the Bureau de Longitudes in addition to his other roles. On 3 September of that year he set out with François Arago to Formentera, in the Balearic Islands, to complete earlier work begun there on calculating the measure of the arc of the meridian. They were still undertaking measurements when, in May 1808, Napoleon declared his brother Joseph Bonaparte as Spanish ruler and the War of Independence began. Biot and Arago must have looked extremely suspicious; two Frenchmen with sophisticated measuring instruments working on Spanish territory. Biot fled back to France immediately. Later in 1808, together with Claude-Louis Mathieu, he embarked on a series of measurements of the length of the seconds pendulum at different points on the meridian, in particular at Bordeaux and at Dunkirk. Both Mathieu and Biot received a prize from the Académie des Sciences in 1809 for this highly accurate work, and in 1812 they received a second prize from the Academy for their achievements. In 1809 Biot was appointed Professor of Physical Astronomy at the Faculty of Sciences. He held this position for over fifty years.

Biot studied a wide range of mathematical topics, mostly on the applied mathematics side. He made advances in astronomy, elasticity, electricity and magnetism, heat and optics on the applied side while, in pure mathematics, he also did important work in geometry. He collaborated with Arago on refractive properties of gases. Biot, together with Felix Savart, discovered that the intensity of the magnetic field set up by a current flowing through a wire varies inversely with the distance from the wire. This is now known as Biot-Savart's Law and is fundamental to modern electromagnetic theory. Morris Kline, reviewing [8], writes:-

Biot depended entirely upon experiments to determine the interaction of a magnet and a straight line of electrical current and then inferred a mathematical law concerning the force between current and magnet.

Light was the topic on which Biot devoted most time, making the major discovery of the laws of rotary polarization by crystalline bodies. Having discovered these laws he used them in analysis of saccharine solutions using an instrument called a polarimeter which he invented. For this work on the polarisation of light passing through chemical solutions he was awarded the Rumford Medal of the Royal Society of London in 1840. He had been elected as a foreign member of the Royal Society in 1815.

One of his important works was Mémoire sur la figure de la terre Ⓣ (1827) which describes the shape of the Earth. Among his other major works we mention: Analyse de la mécanique céleste de M Laplace Ⓣ (1801); Traité analytique des courbes et des surfaces du second degré Ⓣ (1802); Recherches sur l'intégration des équations différentielles partielles et sur les vibrations des surfaces Ⓣ (1803); Essai de géométrie analytique appliqué aux courbes et aux surfaces de second ordre Ⓣ (1806); Recherches expérimentales et mathématiques sur les mouvements des molécules de la lumière autour de leur centre de gravité Ⓣ (1814); Traité de physique experimentale et mathématique Ⓣ (1816); Precis de physique Ⓣ (1817); (with Arago) Recueil d'observations géodésiques, astronomiques et physiques exécutées en Espagne et Écosse Ⓣ (1821); Mémoire sur la vraie constitution de l'atmosphère terrestre Ⓣ (1841); Traité élémentaire d'astronomie physique Ⓣ (1805); Recherches sur plusieurs points de l'astronomie égyptienne Ⓣ (1823); Recherches sur l'ancienne astronomie chinoise Ⓣ (1840); Études sur l'astronomie indienne et sur l'astronomie chinoise Ⓣ (1862); Essai sur l'histoire générale des sciences pendant la Révolution Ⓣ (1803); Discours sur Montaigne Ⓣ (1812); Lettres sur l'approvisionnement de Paris et sur le commerce des grains Ⓣ (1835); Traite d'astronomie physique Ⓣ (1850); and Mélanges scientifiques et littéraires Ⓣ (1858).

He tried twice for the post of Secretary to the Académie des Sciences and to improve his chances for election to this post he wrote Essai sur l'Histoire Générale des Sciences pendant la Révolution. However he lost out in 1822 to Fourier for this post, then again when Fourier died in May 1830 he applied again for the post of Secretary, only to lose to Arago on this occasion. The rivalry between Arago and Biot was again evident in 1839 when different photographic processes were competing [10]:-

Arago and Biot, France's leading authorities in the field of optics, had spent the past thirty years disagreeing about the ability of optical instruments to represent the world. Photography became one more opportunity for them to disagree, and they did not shrink from the task. The debate extended beyond questions of assigning priority and apportioning credit. At its heart was the question of what the photographic surfaces showed, what relation the visible inscription bore to the real world.

Arago supported the Daguerre photographic process with silver plates while Biot championed an approach with paper soaked in a silver solution as developed by Henry Fox Talbot. This was not because he thought this process produced clearer photographs, rather it was because he believed that the images captured 'chemical radiation' invisible to the eye. We should note that the idea of 'chemical radiation' was widely believed at this time. Biot also believed that the photographic process should be one reserved for scientific use and not made available for public use. There was a period of collaboration between Biot and Talbot, the two exchanging letters frequently. Basically the photographic process became another tool for Biot to use in his investigations of light which had always been a major interest to him.

As well as interests in almost every branch of science, Biot was interested in the history of the subject. He published works on this topic such as: Essai sur l'histoire générale des sciences pendant la Révolution française Ⓣ (1803); Notice historique sur la vie et les ouvrages de Newton Ⓣ (1822); Recherches sur plusieurs points de l'astronomie égyptienne appliquées aux monuments astronomiques trouvés en Égypte Ⓣ (1823); Sur la manière de calculer les positions des étoiles relativement à l'équateur et à l'écliptique pour les époques anciennes Ⓣ (1823); Opuscule sur l'Astronomie ancienne des Chinois, des Indous et des Arabes Ⓣ (1840); Mémoire sur le Zodiaque de Denderah Ⓣ (1844); Précis de l'histoire de l'Astronomie planétaire Ⓣ (1847); and Études sur l'astronomie indienne et l'astronomie chinoise Ⓣ (1862).

In [4] St Beuve says that Biot was endowed to the highest degree with all the qualities of curiosity, finesse, penetration, precision, ingenious analysis, method, clarity, in short with all the essential and secondary qualities, bar one, genius, in the sense of originality and invention.

A contrasting comment by Olinthus Gregory in 1821 is:-

With regard to M Biot, I had an opportunity of pretty fully appreciating his character when we were together in the Zetland [= Shetland] Isles; and I do not hesitate to say that I never met so strange a compound of vanity, impetuosity, fickleness, and natural partiality, as is exhibited in his character.

In addition to the honours we mentioned above, Biot was also honoured by being made Chevalier of the Legion of Honour in 1814 and Commander in 1849. He was elected to the to the Academy of Inscriptions and Belles-Lettre in 1841 and to the French Academy in 1856.