The concept of isothermic lines is not attributed to a single person. Instead, it emerged as a natural consequence of the development of thermodynamics and the understanding of heat transfer.

Here's a breakdown:

* Early Understanding of Heat: Before the development of thermodynamics, people had a basic understanding of heat and temperature. They knew that heat flowed from hotter objects to colder ones.

* Development of Thermodynamics: In the 19th century, scientists like James Prescott Joule, Rudolf Clausius, and William Thomson (Lord Kelvin) laid the foundations of thermodynamics. They established the relationship between heat, work, and internal energy.

* Isothermic Lines: The concept of isothermal lines arose naturally from the understanding of heat transfer and temperature gradients. Isothermal surfaces are simply surfaces where the temperature remains constant.

Therefore, while no single individual is credited with "discovering" isothermic lines, their understanding and importance stemmed from the collective efforts of scientists who developed the field of thermodynamics.

Here are some key figures who contributed to the understanding of heat transfer and temperature gradients:

* Joseph Fourier (1768-1830): Developed Fourier's Law, which describes the heat conduction process.

* James Clerk Maxwell (1831-1879): Developed the kinetic theory of gases, which helped explain the relationship between temperature and the movement of molecules.

* Ludwig Boltzmann (1844-1906): Further developed the kinetic theory and established the statistical interpretation of thermodynamics.

In summary: The concept of isothermic lines is a fundamental consequence of our understanding of heat transfer and thermodynamics, not a singular invention. It developed gradually as the understanding of these fields progressed.