  Certain linear objects, termed physical lines, are considered, and initial
assumptions concerning their properties are introduced. A physical line in the
form of a circle is called a \emph{$J$-string}. It is assumed that a $J$-string
has an angular momentum whose value is $\hbar$. It is then established that a
$J$-string of radius $R$ possesses a mass $m_J$, equal to $h/2\pi c R$, a
corresponding energy, as well as a charge $q_J$, where $q_J = (hc/2\pi)^{1/2}$.
It is shown that this physical curve consists of indivisible line segments of
length $\ell_\Delta = 2\pi(hG/c^3)^{1/2}$, where $c$ is the speed of light and
$G$ is the gravitational constant. Quantum features of $J$-strings are studied.
Based upon investigation of the properties and characteristics of $J$-strings,
a method is developed for the computation of the Planck length and mass
$(\ell^*_P, m^*_P)$. The values of $\ell^*_P$ and $m^*_P$ are computed
according to the resulting formulae (and given in the paper); these values
differ from the currently accepted ones.
