菲利克斯·沙伐Félix Savart

菲利克斯·沙伐的父亲是Gérard 沙伐，他是一名工程师。这个家族与Mézières有着长期的联系，Gérard的父亲（沙伐的祖父）也是该城本地人，曾参与1748年当地工程学校的创办。Gérard 沙伐搬到Metz，在那里负责工程学校的绘图员。沙伐和他的哥哥Nicolas（生于1790年）在Metz接受早期教育。由于家族有参与军事工程学校的浓厚传统，人们可能会以为沙伐也会走上这条路。事实上，他早期的训练确实把他引向那个方向，但在1808年，十七岁时，他决定接受医学职业的训练。

沙伐从1808年到1810年大约两年时间在Metz的一家医院学习。当然，他成长于法国在拿破仑统治下享受军事胜利的时期，拿破仑在1792年至1797年间率领法国军队战胜了奥地利、普鲁士、英国、西班牙和荷兰的军队。对为遏制法国势力而组建的另外三个联盟的胜利，使拿破仑在1810年达到权力巅峰。正是在这个时候，在Metz医院接受培训之后，沙伐成为拿破仑军队中的团级外科医生。他确实遵循了某些家族传统，在第一工兵营服役。然而，在他1810年至1814年服役的这些年里，拿破仑在西班牙和俄国战役中遭受失败。1814年，沙伐从军队退役，重新开始他的医学训练。

沙伐于1814年前往斯特拉斯堡，两年后，他从该大学获得医学学位。他的学位论文题目是静脉曲张。在医学学习期间，沙伐对Aulus Cornelius Celsus（公元一世纪）产生了兴趣，他是最伟大的罗马医学作家之一，著有De medicina Ⓣ（《论医学》）。完成学位后，沙伐留在斯特拉斯堡，在那里他既获得了进一步的医学经验，也从事Celsus的De medicina Ⓣ（《论医学》）的翻译工作。1817年回到Metz并开设诊所后，沙伐花在物理学研究上的时间比治疗病人的时间还多。他建立了一个出色的物理实验室来进行实验，并迷上了对声音的研究，特别是小提琴等乐器的声学。他开始制作小提琴，试图将乐器的形式建立在数学原理之上。

沙伐对他的医疗实践兴趣寥寥，患者也无意前来就诊，于是他决定在1819年前往巴黎，为他的塞尔苏斯De medicinaⓉ（《论医学》）译本寻找出版商。他前往巴黎还有另一个原因，那就是去见让-巴蒂斯特·毕奥，以便与他讨论当时令沙伐着迷的乐器声学。碰巧的是，当沙伐抵达巴黎时，让-巴蒂斯特·毕奥正在理学院讲授声学。他发现沙伐关于弓弦乐器声学的工作非常有趣，于是将沙伐撰写的一篇论文Mémoire des instruments à chordes et à archetⓉ（《关于带弓弦乐器的论文》）提交给科学院；该论文于1819年发表。这篇论文包含一种梯形小提琴的设计，沙伐声称其声学性能优于传统小提琴。他使用了与克拉尼类似的技术所获得的实验结果。人们有理由问，他的梯形小提琴有多成功。多斯特罗夫斯基写道[1]：-

当这件乐器在一个包括让-巴蒂斯特·毕奥、作曲家凯鲁比尼以及科学院和美术学院的其它成员在内的委员会面前演奏时，其音色被评判为极其清晰均匀，但略显柔和。

沙伐抵达巴黎时，让-巴蒂斯特·毕奥除了讲授声学外，还在进行电学研究。两人开始了合作，当1820年初汉斯·克里斯蒂安·奥斯特报告说，放置在载流导线附近的罗盘指针指向与导线成直角时，他们开始更深入地研究导线产生的场。利用磁偶极子的振荡来确定载流导线附近的场强，他们发现了今天所谓的让-巴蒂斯特·毕奥-沙伐定律。电流产生的磁场可以用让-巴蒂斯特·毕奥-沙伐定律来计算，他们于1820年10月30日向科学院提交了该定律。他们把磁性视为基本属性，而不是采用安德烈-马里·安培的方法，后者将其视为源自电路。一篇让-巴蒂斯特·毕奥-沙伐的联合论文Note sur le magnétisme de la pile de VoltaⓉ（《关于伏打电堆的磁性》）于1820年发表在Annales de chemie et de physique上。

让-巴蒂斯特·毕奥帮助沙伐在巴黎找到了一份教职，从1820年起他在那里的一所私立学校教授科学。1827年11月5日，沙伐当选为科学院物理学部成员，接替于当年7月去世的奥古斯丁·菲涅耳。他从1828年起在法兰西学院任教，接替安德烈-马里·安培成为那里的实验物理学教授。他一直担任此职直到1841年去世，距他五十岁生日仅差几个月。

除了上面提到的1819年论文外，沙伐还进行了关于声音的实验，这些实验对后来的声学研究者很重要。在他就这一主题发表的其他论文中，我们提到Mémoire sur la communication des mouvements vibratoires entre les corps solidesⓉ（关于固体之间振动运动传递的回忆录）（1820年）、Recherches sur les vibrations de l'airⓉ（关于空气振动的研究）（1823年）和Mémoire sur les vibrations des corps solides, considérées en généralⓉ（关于固体振动的一般考虑回忆录）（1824年）。他对音乐的贡献总结在Grove的Dictionary of Music and Musicians[2]中：-

总的来说，他阐明了作为声源的振动体与与其相连的其他物体之间复杂关系的本质，凭借这种关系，原始声音的强度被放大，音质被改变，这种安排的著名例子由小提琴族和钢琴的音板提供。

他还开发了沙伐圆盘，这是一种产生已知频率声波的装置，使用旋转的齿轮作为测量设备。McKusick和Wiskind写道[5]：-

大约1830年，沙伐发明了一种齿轮，用于确定给定音乐音调中的振动次数。他将硬纸板舌片附在轮的箍上，并安排这些在轮转动时撞击一个突出物体。或者，他让轮的齿轮撞击硬纸板舌片。据推测，他使用这种仪器来确定他从实验模型中引出的音调每秒的振动次数。他会加快轮的旋转，直到产生与实验音调匹配的音调。由于轮产生的音调频率可以很容易地确定，模型产生的未知音调的频率就被确定了。通过这种方法的扩展，沙伐复合了音乐音符。例如，他会结合使用齿数彼此有简单关系的轮。他使用这种方法来探索和谐和不和谐声音的物理基础。

还有其他主题让沙伐感兴趣，并进行了研究。例如，他研究了湍流，其研究的医学意义在[5]中详细研究。作者在总结中写道：-

在19世纪后半叶，关于心脏杂音起源的医学和生理学著作中，沙伐的“流体静脉”被反复提及。当人们意识到，在血液流动部分阻塞的情况下，杂音不是在阻塞部位或其近端产生，而是在其后的流体中产生时，人们推测涉及一种像沙伐所揭示的机制。

论文[4]讨论了当圆柱形射流以垂直于圆盘的速度冲击时水钟存在的详细实验研究，这最早由沙伐在1833年研究。

让我们以两个后记结束这本传记。首先让我们注意，尽管沙伐去巴黎的主要目标之一是出版他对Celsus的De medicina的翻译，但这部作品从未出现。看来沙伐转向了更有趣的方向。作为第二个后记，我们注意到关于沙伐的哥哥Nicolas Savart的一些事实。与沙伐不同，Nicolas在巴黎综合理工学院学习，然后遵循家族传统成为工程兵团的军官。在这个后记中提到他的原因是，Nicolas像他的兄弟一样，也发表了关于声学的论文。例如，他发表了Quelques faits résultant de la réflexion des ondes sonoresⓉ（声波反射产生的一些事实）（1839年），以及在沙伐去世后至少三篇进一步的论文。

沙伐获得荣誉，在Mézières有一条以他命名的街道。

Félix Savart's father was Gérard Savart who was an engineer. The family had a long association with Mézières, Gérard's father (Félix's paternal grandfather), also a native of that city, had been involved with the founding of the engineering school there in 1748. Gérard Savart moved to Metz where he was in charge of draftsmen at the engineering school. Félix and his older brother Nicolas (born 1790) had their early schooling in Metz. With a strong family tradition of involvement with military engineering schools, one might have expected Félix Savart to also go down that path. In fact his early training did take him in that direction but in 1808, at the age of seventeen, he decided to train for a career in medicine.

Savart spent around two years from 1808 to 1810 studying at a hospital in Metz. Of course he had grown up in a period when France was enjoying military victories under Napoleon who had led French armies to victories over the armies of Austria, Prussia, Great Britain, Spain and the Netherlands between 1792 and 1797. Victories over three further coalitions set up to try to curb French power saw Napoleon at the height of his power in 1810. It was at this time, after training in the Metz hospital, that Savart became a regimental surgeon in Napoleon's army. He did follow certain family traditions by serving in the first battalion of engineers. However, during the years in which he served from 1810 to 1814, Napoleon suffered defeats in the Spanish and Russian campaigns. In 1814 Savart was discharged from the army and resumed his medical training.

It was to Strasbourg that Savart went in 1814 and, two years later, he graduated from the university with a medical degree. The topic for his thesis was varicose veins. During his medical studies Savart became interested in Aulus Cornelius Celsus (first century AD), one of the greatest Roman medical writers, author of De medicina Ⓣ. After completing his degree Savart remained in Strasbourg where he both gained further medical experience and also worked on a translation of Celsus's De medicina Ⓣ. After returning to Metz in 1817 where he set up a medical practice, Savart spent more time studying physics than treating patients. He set up an excellent physics laboratory to carry out experiments and became fascinated with a study of sound, in particular the acoustics of musical instruments such as the violin. He began to build violins trying to base the form of the instrument on mathematical principles.

With Savart showing little interest in his medical practice, and patients showing little interest in joining, he decided to go to Paris in 1819 and seek a publisher for his translation of Celsus's De medicina Ⓣ. He had another reason to go to Paris, and that was to see Biot so that he could discuss with him the acoustics of musical instruments that was by now fascinating Savart. As it happened, at the time that Savart reached Paris Biot was lecturing on acoustics at the Faculty of Science. He found Savart's work on the acoustics of bowed string instruments very interesting and he presented a memoir that Savart had written Mémoire des instruments à chordes et à archet Ⓣ to the Academy of Sciences; it was published in 1819. This memoir contained a design of a trapezoid violin which Savart claimed to have superior acoustic performance to the traditional violin. He used experimental results achieved using techniques similar to those of Chladni. It is reasonable to ask how successful he was with his trapezoid violin. Dostrovsky writes [1]:-

When the instrument was played before a committee that included Biot, the composer Cherubini, and other members of the Academy of Sciences and the Académie des Beaux-Arts, its tone was judged as extremely clear and even, but somewhat subdued.

When Savart arrived in Paris, Biot was undertaking research on electricity in addition to lecturing on acoustics. The two began a collaboration and when, early in 1820, Hans Christian Oersted reported that a compass needle placed near a wire carrying current pointed at right angles to the wire, they began to research more deeply into the field produced by the wire. Using the oscillation of a magnetic dipole to determine the strength of the field close to a wire carrying current, they discovered what today is called the Biot-Savart law. Magnetic fields produced by electric currents can be calculated using the Biot-Savart law which they presented to the Academy of Sciences on 30 October 1820. They took magnetism as the fundamental property rather than using the approach due to Ampère which treated it as derived from electric circuits. A joint Biot-Savart paper Note sur le magnétisme de la pile de Volta Ⓣ was published in the Annales de chemie et de physique in 1820.

Biot helped Savart find a teaching position in Paris and from 1820 he taught science in a private school there. On 5 November 1827, Savart was elected to the physics section of the Academy of Sciences to replace Fresnel who had died in July of that year. He taught at the Collège de France from 1828, becoming a professor of experimental physics there to succeed Ampère. He continued to hold this position until his death in 1841, a few months short of his fiftieth birthday.

In addition to the 1819 paper we mentioned above, Savart also carried out experiments on sound which became important for later students of acoustics. Among other papers he published on this topic we mention Mémoire sur la communication des mouvements vibratoires entre les corps solides Ⓣ (1820), Recherches sur les vibrations de l'air Ⓣ (1823), and Mémoire sur les vibrations des corps solides, considérées en général Ⓣ (1824). His contributions to music are summed up in Grove's Dictionary of Music and Musicians [2]:-

In general he threw light on the nature of the complicated relation between a vibrating body which is the source of sound and other bodies brought into connection with it, by virtue of which the original sound is magnified in intensity and modified in quality, well-known examples of such an arrangement being furnished by the sounding board of the violin tribe and the pianoforte.

He also developed the Savart disk, a device which produced a sound wave of known frequency, using a rotating cog wheel as a measuring device. McKusick and Wiskind write [5]:-

About 1830 Savart invented a toothed wheel for determining the number of vibrations in a given musical tone. He attached tongues of pasteboard to a hoop of the wheel and arranged for these to strike a projecting object as the wheel was turned. Alternately, he had cogs of a wheel strike a tongue of pasteboard. Presumably he employed this instrument to determine the vibrations per second of the tones he elicited from his experimental models. he would speed up the rotation of the wheel until a tone which matched the experimental one was produced. Since the frequency of the tone produced by the wheel could be easily determined, the frequency of the unknown tone produced by the model was ascertained. by an extension of this method, Savart compounded musical notes. For example, he would use, in combination, wheels with numbers of teeth which bore a simple relationship to each other. he used this method to explore the physical basis of harmonious and discordant sounds.

There were other topics that interested Savart and on which he undertook research. For example he studied turbulence and the medical implications of his research is studied in detail in [5]. The authors write in summary:-

In the latter half of the nineteenth century, in medical and physiological writings on the genesis of heart murmurs, Savart's "fluid veins" were repeatedly referred to. When it was realised that, in the case of partial obstruction to the flow of blood, the murmur is produced not at, or proximal to, the site of obstruction but in the fluid beyond, it was presumed that a mechanism like that revealed by Savart was involved.

The paper [4] discusses a detailed experimental study of the existence of water bells when a cylindrical jet impacts with the velocity normal to a circular disc, which was first studied by Savart in 1833.

Let us end this biography with giving two postscripts. First let us note that although one of Savart's main aims in going to Paris was to publish his translation of Celsus's De medicina the work never appeared. It seems that Savart became diverted into more interesting directions. As a second postscript we note some facts about Savart's older brother Nicolas Savart. Unlike Félix, Nicolas studied at the École Polytechnique and then followed the family tradition of becoming an officer in the engineering corps. The reason for mentioning him in this postscript is that Nicolas, like his brother, also published papers on acoustics. For example he published Quelques faits résultant de la réflexion des ondes sonores Ⓣ (1839), and at least three further papers after the death of Félix.

Félix Savart was honoured by having a street in Mézières named after him.