Regard an element of the set $$\Delta := {(x_1, x_2, \dots): x_1
\geq x_2 \geq \dots \geq 0, \Sigma_i x_i = 1}$$ as a fragmentation of unit mass
into clusters of masses $x_i$. The additive coalescent of Evans and Pitman is
the $\Delta$-valued Markov process in which pairs of clusters of masses ${x_i,
x_j}$ merge into a cluster of mass $x_i + x_j$ at rate $x_i + x_j$. They showed
that a version $(\rm X^{\infty}(t), -\infty < t < \infty)$ of this
process arises as a $n \to \infty$ weak limit of the process started at time
$-1/2 \log n$ with $n$ clusters of mass $1/n$. We show this standard
additive coalescent may be constructed from the continuum random tree of Aldous
by Poisson splitting along the skeleton of the tree. We describe the
distribution of $\rm X^{\infty}(t)$ on $\Delta$ at a fixed time $t$. We
show that the size of the cluster containing a given atom, as a process in
$t$, has a simple representation in terms of the stable subordinator of
index 1/2. As $t \to -\infty$, we establish a Gaussian limit for (centered and
normalized) cluster sizes and study the size of the largest cluster.