夏尔·奥古斯丁·德·库仑Charles-Augustin de Coulomb

夏尔·奥古斯丁·德·库仑的父亲是Henry Coulomb，母亲是凯瑟琳·巴杰。他的父母都来自各自领域内知名的家庭。他父亲的家族在法律职业和法国朗格多克地区的行政管理中很重要，他母亲的家族也相当富有。在法国西南部昂古穆瓦首府昂古莱姆长大后，库仑一家搬到了巴黎。在巴黎，他进入了马扎林学院，在那里他接受了语言、文学和哲学方面的良好古典基础训练，并接受了数学、天文学、化学和植物学方面最好的教学。

在他教育的这个阶段，库仑遭遇了一场危机。尽管他父亲地位良好，但他进行了不成功的金融投机，失去了所有的钱，从巴黎搬到了蒙彼利埃。库仑的母亲留在巴黎，但库仑在职业方向上与她发生了分歧，所以他离开了巴黎，去蒙彼利埃与父亲同住。在这个阶段，库仑的兴趣主要在数学和天文学上，在蒙彼利埃期间，他于1757年3月加入了那里的科学学会，并向学会宣读了几篇关于这些主题的论文。

库仑想进入梅济耶尔的工程学校，但意识到要想成功通过入学考试，他需要接受辅导。1758年10月，他前往巴黎接受参加考试所必需的辅导。夏尔·艾蒂安·路易·加缪已于1755年被任命为炮兵学校的考官，正是他的Cours de mathématiquesⓉ（《数学教程》）被库仑研读了数月。1758年，库仑参加了由夏尔·艾蒂安·路易·加缪设置的考试并通过，于1760年2月进入梅济耶尔的工程学校。大约在这段时间里，他建立了一些重要的人脉关系，这些关系对他后来的科学工作至关重要，其一是与他在梅济耶尔的老师夏尔·博叙，其二是与让-夏尔·德博尔达。

库仑于1761年11月毕业。此时他已是一名训练有素的工程师，在工程兵团中拥有中尉军衔。在接下来的二十年里，他被派往各种不同的地方，从事工程、结构设计、防御工事、土力学以及许多其他领域的工作。他的第一个岗位是布雷斯特，但在1764年2月，他被派往西印度群岛的马提尼克岛。1658年，马提尼克岛在路易十四统治下归入法国主权。然而，在随后的岁月里，马提尼克岛遭到了多支外国舰队的攻击。1674年荷兰人进攻该岛但被击退，1693年英国人也是如此，1759年英国人再次被击退。马提尼克岛最终于1762年被英国人占领，但根据1763年《巴黎条约》的条款归还给法国。法国人随后试图通过建造一座新堡垒来使该岛更加安全。

库仑被指派负责建造新的波旁堡，这项任务一直占据着他的时间，直到1772年6月。在此期间，他展示了组织施工所需的工程技能的实践方面，但他的经历在他后来撰写的力学理论回忆录中发挥了重要作用。就库仑的健康而言，这些年是艰难的，他在马提尼克岛期间所患的疾病使他的余生健康状况不佳。

回到法国后，库仑被派往Bouchain。然而，他现在开始撰写关于应用力学的重要著作，并于1773年在巴黎向Académie des Sciences提交了他的第一部作品。这部作品Sur une application des règles, de maximis et minimis à quelque problèmes de statique, relatifs à l'architecture Ⓣ（关于将极大极小规则应用于与建筑相关的某些静力学问题）是（用库仑的话说，例如见[1]）这样写的：-

……在数学和物理学的结合所能允许的范围内，确定摩擦和 cohesion 在静力学某些问题中的影响。

从数学的角度来看，这篇论文最重要的事实也许是库仑运用变分法来解决工程问题。正如1中所写：-

在这篇1773年的论文中，几乎有令人应接不暇的丰富内容，因为库仑接着讨论了砖石桥墩全面破裂理论、拱顶设计和土压力理论。在最后一项中，他发展了土力学中广义滑动楔体理论，这一理论至今仍在基础工程实践中使用。库仑这部分工作相对被忽视的一个原因也许是，他试图展示变分法在构建结构力学基本问题处理方法中的应用，而不是给出具体问题的数值解。

情况往往是，在大多数人数学素养较低的领域中应用数学的成熟方法，会使这项工作具有当时不常见的长远价值。这篇论文确实受到Académie des Sciences的高度重视，因为它使他在1774年7月6日被任命为夏尔·博叙的通讯院士。从布尚，库仑接下来被派往瑟堡。在那里期间，他写了一篇关于磁性罗盘的著名论文，并于1777年提交给Académie des Sciences的大奖赛。

这篇1777年的论文为库仑赢得了部分奖金，其中包含他关于扭秤的第一项工作[1]：-

……他对圆柱体扭转问题的简单、优雅的解法，以及他在物理应用中扭秤的使用，对随后许多年的众多物理学家都很重要。……库仑发展了细丝和毛发扭转理论。在这里，他首次展示了扭转悬挂如何为物理学家提供一种精确测量极小力的方法。

库仑在瑟堡期间还发生了另一个有趣的事件。罗贝尔-雅克·杜尔哥于1774年8月24日被路易十六任命为财政总监。1775年，他开始感到受到政治对手的威胁，并开始了一系列改革。其中包括对工程兵团的改革，杜尔哥征集关于其可能重组的论文。库仑提交了一篇论文，阐述了他的想法，这是一个了解他政治观点的绝佳机会。库仑希望国家和个人发挥同等作用。他提议，工程兵团特别是所有公共服务部门，在组织内部晋升时应承认其个别成员的才能。

1779年，库仑被派往罗什福尔，与蒙塔朗贝尔侯爵合作，在艾克斯岛附近建造一座完全用木头制成的堡垒。与库仑一样，蒙塔朗贝尔侯爵以设计防御工事的军事工程师而闻名，但他的创新工作受到了许多法国工程师的批评[2]：-

蒙塔朗贝尔将堡垒视为不过是为了向进攻军队倾泻压倒性火力的巨大永久炮台，他简化了沃邦复杂的几何设计，依赖于简单的多边形结构，通常使用分离的外围堡垒而不是突出的棱堡。

在罗什福尔期间，库仑继续他的力学研究，特别是利用罗什福尔的造船厂作为他实验的实验室。他在罗什福尔对摩擦的研究导致了库仑关于摩擦的主要著作Théorie des machines simplesⓉ（简单机器理论），这使他在1781年获得了Académie des Sciences的大奖。在这篇论文中库仑[1]：-

...研究了滑动表面的静态和动态摩擦以及绳索弯曲和滚动中的摩擦。通过对许多物理参数的检查，他发展了一系列二项方程，第一项是常数，第二项随时间、法向力、速度或其他参数变化。

由于这项获奖工作，[5]的作者写道：-

库仑对摩擦科学的贡献异常巨大。毫不夸张地说，他创造了这门科学。

事实上，1781年的这篇回忆录改变了库仑的一生。由于这项工作，他当选为Académie des Sciences力学部的成员，并迁往巴黎，在那里获得了一个永久职位。他此后再也没有承担任何工程项目，尽管他仍然担任工程事务的顾问，并且从那时起，他将毕生精力投入到物理学而非工程学。他在1785年至1791年间向Académie des Sciences提交了七篇关于电学和磁学的重要论文。这七篇论文在[6]中进行了讨论，作者在其中表明库仑：-

……通过使用扭秤方法获得了一些显著的结果：吸引和排斥定律、电点电荷、磁极、带电体表面上的电荷分布等。库仑定律对电磁学发展的重要性得到了考察和讨论。

在这些论文中，他发展了同种和异种电荷物体之间吸引和排斥的理论。他证明了这类力的平方反比定律，并进一步考察了理想导体和电介质。他提出不存在理想的电介质，认为每种物质都有一个极限，超过该极限就会导电。这些基础性论文提出了电荷之间超距作用的观点，类似于艾萨克·牛顿的引力理论基于质量之间的超距作用。

这些关于电和磁的论文，尽管是库仑在这一时期最重要的工作，但只是他所承担工作的一小部分。他在1781年至1806年间向Académie des Sciences提交了二十五篇论文。库仑在这一时期与夏尔·博叙、让-夏尔·德博尔达、de Prony和皮埃尔·西蒙·拉普拉斯密切合作。值得注意的是，他参与了科学院310个委员会的工作。他仍然作为顾问参与工程项目，其中最引人注目的是他在1783-84年关于布列塔尼运河和港口改进的报告。他违背自己的更好判断被迫承担这项任务，最终在受到批评时承担了责任，并于1783年11月在监狱中度过了一个星期。

他还在教育和医院改革等不同领域为各自的法国政府提供服务。1787年，他前往英国报告伦敦医院的情况。1784年7月，他被任命管理皇家喷泉，并负责巴黎大部分供水。1790年2月26日，库仑的第一个儿子出生，尽管他没有与他儿子的母亲Louise Françoise LeProust Desormeaux结婚。

当1789年法国大革命开始时，库仑已深入参与他的科学工作。许多机构被重组，并非所有都令库仑满意，他于1791年从工程兵团退休。大约在Académie des Sciences于1783年8月被废除的同时，他被免去了负责供水的职务，并且在1793年12月，他所服务的度量衡委员会也被解散。库仑和让-夏尔·德博尔达退隐到乡下，在他拥有的布卢瓦附近的房子里进行科学研究。

Académie des Sciences被法兰西学院取代，库仑在1795年12月被选入学院后返回巴黎。1797年7月30日，他的第二个儿子出生，1802年，他与两个儿子的母亲Louise Françoise LeProust Desormeaux结婚。我们上面提到库仑参与了教育服务。这些主要是在1802年至1806年间，当时他是公共教育总监，在这个角色中，他主要负责在法国各地建立中学。

让我们以引用让-巴蒂斯特·毕奥对他的赞词作为结束，他写道：-

正是归功于让-夏尔·德博尔达和库仑，法国才迎来了真正物理学的复兴，不是冗长而假设性的物理学，而是那种巧妙而精确的物理学，它严格地观察和比较一切。

Charles Augustin Coulomb's father was Henry Coulomb and his mother was Catherine Bajet. Both his parents came from families which were well known in their fields. His father's family were important in the legal profession and in the administration of the Languedoc region of France, and his mother's family were also quite wealthy. After being brought up in Angoulême, the capital of Angoumois in southwestern France, Coulomb's family moved to Paris. In Paris he entered the Collège Mazarin, where he received a good classical grounding in language, literature, and philosophy, and he received the best available teaching in mathematics, astronomy, chemistry and botany.

At this stage in his education there was a crisis for Coulomb. Despite his father's good standing, he had made unsuccessful financial speculations, had lost all his money and moved from Paris to Montpellier. Coulomb's mother remained in Paris but Coulomb had a disagreement with her over the direction his career should take so he left Paris and went to Montpellier to live with his father. At this stage Coulomb's interests were mainly in mathematics and astronomy and while in Montpellier he joined the Society of Sciences there in March 1757 and read several papers on these topics to the Society.

Coulomb wanted to enter the École du Génie at Mézières but realised that to succeed in passing the entrance examinations he needed to be tutored. In October 1758 he went to Paris to receive the tutoring necessary to take the examinations. Camus had been appointed as examiner for artillery schools in 1755 and it was his Cours de mathématiques Ⓣ that Coulomb studied for several months. In 1758 Coulomb took the examinations set by Camus which he passed and he entered the École du Génie at Mézières in February 1760. He formed a number of important friendships around this time which were important in his later scientific work, one with Bossut who was his teacher at Mézières and the other with Borda.

Coulomb graduated in November 1761. He was now a trained engineer with the rank of lieutenant in the Corps du Génie. Over the next twenty years he was posted to a variety of different places where he was involved in engineering, in structural design, fortifications, soil mechanics, and many other areas. His first posting was to Brest but in February 1764 he was set to Martinique in the West Indies. Martinique fell under the sovereignty of France under Louis XIV in 1658. However Martinique was attacked by a number of foreign fleets over the following years. The Dutch attacked it in 1674 but were driven off, as were the English in 1693 and the English again in 1759. Martinique was finally captured by the English in 1762 but were returned to France under the terms of the Treaty of Paris in 1763. The French then made attempts to make the island more secure by building a new fort.

Coulomb was put in charge of the building of the new Fort Bourbon and this task occupied him until June 1772. It was a period during which he showed the practical side of his engineering skills which were needed to organise the construction, but his experiences would play a major role in the later theoretical memoirs he wrote on mechanics. As far as Coulomb's health was concerned these were difficult years and the illnesses which he suffered while on Martinique left him in poor health for the rest of his life.

On his return to France, Coulomb was sent to Bouchain. However, he now began to write important works on applied mechanics and he presented his first work to the Académie des Sciences in Paris in 1773. This work, Sur une application des règles, de maximis et minimis à quelque problèmes de statique, relatifs à l'architecture Ⓣ was written (in Coulomb's words, see for example [1]):-

... to determine, as far as a combination of mathematics and physics will permit, the influence of friction and cohesion in some problems of statics.

Perhaps the most significant fact about this memoir from a mathematical point of view is Coulomb's use of the calculus of variations to solve engineering problems. As Gillmor writes in [1]:-

In this one memoir of 1773 there is almost an embarrassment of riches, for Coulomb proceeded to discuss the theory of comprehensive rupture of masonry piers, the design of vaulted arches, and the theory of earth pressure. In the latter he developed a generalised sliding wedge theory of soil mechanics that remains in use today in basic engineering practice. A reason, perhaps, for the relative neglect of this portion of Coulomb's work was that he sought to demonstrate the use of variational calculus in formulating methods of approach to fundamental problems in structural mechanics rather than to give numerical solutions to specific problems.

It is often the case that a sophisticated use of mathematics in an application to an area where most have less mathematical sophistication, gives the work a long term values which is not often seen at the time. The memoir was certainly highly valued by the Académie des Sciences for it led to him being named as Bossut's correspondent on 6 July 1774. From Bouchain, Coulomb was next posted to Cherbourg. While he was there he wrote a famous memoir on the magnetic compass which he submitted for the Grand Prix of the Académie des Sciences in 1777.

This 1777 paper won Coulomb a share of the prize and it contained his first work on the torsion balance [1]:-

... his simple, elegant solution to the problem of torsion in cylinders and his use of the torsion balance in physical applications were important to numerous physicists in succeeding years. ... Coulomb developed a theory of torsion in thin silk and hair threads. Here he was the first to show how the torsion suspension could provide physicists with a method of accurately measuring extremely small forces.

Another interesting episode occurred during the time which Coulomb spent at Cherbourg. Robert-Jacques Turgot was appointed comptroller general by Louis XVI on 24 August 1774. He began to feel threatened by his political opponents in 1775 and began a series of reforms. Among these was the reform of the Corps du Génie and Turgot called for memoirs on its possible reorganisation. Coulomb submitted a memoir giving his ideas and it is a fascinating opportunity to understand his political views. Coulomb wanted the state and the individual to play equal roles. He proposed that the Corps du Génie in particular, and all public service in general, should recognise the talents of its individual members in promotion within the organisation.

In 1779 Coulomb was sent to Rochefort to collaborate with the Marquis de Montalembert in constructing a fort made entirely from wood near Ile d'Aix. Like Coulomb, the Marquis de Montalembert had a reputation as a military engineer designing fortifications, but his innovative work had been criticised by many French engineers [2]:-

Viewing fortresses as nothing more than immense permanent batteries designed to pour overwhelming fire on attacking armies, Montalembert simplified the intricate geometric designs of Vauban and relied on simple polygonal structures, often with detached peripheral forts instead of projecting bastions.

During his time at Rochefort, Coulomb carried on his research into mechanics, in particular using the shipyards in Rochefort as laboratories for his experiments. His studies into friction in Rochefort led to Coulomb's major work on friction Théorie des machines simples Ⓣ which won him the Grand Prix from the Académie des Sciences in 1781. In this memoir Coulomb [1]:-

... investigated both static and dynamic friction of sliding surfaces and friction in bending of cords and in rolling. From examination of many physical parameters, he developed a series of two-term equations, the first term a constant and the second term varying with time, normal force, velocity, or other parameters.

Because of this prize winning work, the authors of [5] write:-

Coulomb's contributions to the science of friction were exceptionally great. Without exaggeration, one can say that he created this science.

In fact this 1781 memoir changed Coulomb's life. He was elected to the mechanics section of the Académie des Sciences as a result of this work, and he moved to Paris where he now held a permanent post. He never again took on any engineering projects, although he did remain as a consultant on engineering matters, and he devoted his life from this point on to physics rather than engineering. He wrote seven important treatises on electricity and magnetism which he submitted to the Académie des Sciences between 1785 and 1791. These seven papers are discussed in [6] where the author shows that Coulomb:-

... had obtained some remarkable results by using the torsion balance method: law of attraction and repulsion, the electric point charges, magnetic poles, distribution of electricity on the surface of charged bodies and others. The importance of Coulomb's law for the development of electromagnetism is examined and discussed.

In these he developed a theory of attraction and repulsion between bodies of the same and opposite electrical charge. He demonstrated an inverse square law for such forces and went on to examine perfect conductors and dielectrics. He suggested that there was no perfect dielectric, proposing that every substance has a limit above which it will conduct electricity. These fundamental papers put forward the case for action at a distance between electrical charges in a similar way as Newton's theory of gravitation was based on action at a distance between masses.

These papers on electricity and magnetism, although the most important of Coulomb's work over this period, were only a small part of the work he undertook. He presented twenty-five memoirs to the Académie des Sciences between 1781 and 1806. Coulomb worked closely with Bossut, Borda, de Prony, and Laplace over this period. Remarkably he participated in the work of 310 committees of the Academy. He still was involved with engineering projects as a consultant, the most dramatic of which was his report on canal and harbour improvements in Brittany in 1783-84. He had been pressed into this task against his better judgement and he ended up taking the blame when criticisms were made and he spent a week in prison in November 1783.

He also undertook services for the respective French governments in such varied fields as education and reform of hospitals. In 1787 he made a trip to England to report on the conditions in the hospitals of London. In July 1784 he was appointed to look after the royal fountains and took charge of a large part of the water supply of Paris. On 26 February 1790 Coulomb's first son was born, although he was not married to Louise Françoise LeProust Desormeaux who was the mother of his son.

When the French Revolution began in 1789 Coulomb had been deeply involved with his scientific work. Many institutions were reorganised, not all to Coulomb's liking, and he retired from the Corps du Génie in 1791. At about the same time that the Académie des Sciences was abolished in August 1783, he was removed from his role in charge of the water supply and, in December 1793, the weights and measures committee on which he was serving was also disbanded. Coulomb and Borda retired to the country to do scientific research in a house he owned near Blois.

The Académie des Sciences was replaced by the Institut de France and Coulomb returned to Paris when he was elected to the Institute in December 1795. On 30 July 1797 his second son was born and, in 1802, he married Louise Françoise LeProust Desormeaux, the mother of his two sons. We mentioned above that Coulomb was involved with services to education. These were largely between 1802 and 1806 when he was inspector general of public instruction and, in that role, he was mainly responsible for setting up the lycées across France.

Let us end with quoting the tribute paid to him by Biot who wrote:-

It is to Borda and to Coulomb that one owes the renaissance of true physics in France, not a verbose and hypothetical physics, but that ingenious and exact physics which observes and compares all with rigour.