diff --git a/src/FastMultipole.jl b/src/FastMultipole.jl
index f2491db..9ace2f1 100644
--- a/src/FastMultipole.jl
+++ b/src/FastMultipole.jl
@@ -17,6 +17,6 @@ for file in ["containers", "complex", "derivatives", "element", "tree", "direct"
     include(file*".jl")
 end
 
-export fmm!, direct!, Tree, SortWrapper, ProbeSystem, reset!, DerivativesSwitch
+export fmm!, direct!, Tree, SortWrapper, ProbeSystem, add_line!, reset!, DerivativesSwitch
 
 end # module
diff --git a/src/probe.jl b/src/probe.jl
index 332ae0f..f77e223 100644
--- a/src/probe.jl
+++ b/src/probe.jl
@@ -107,6 +107,35 @@ end
 
 reset!(::Nothing) = nothing
 
+"""
+    add_line!(probes::ProbeSystem, x1, x2, n_probes, i_last)
+
+Adds `n_probes` probes in a line between `x1` and `x2`. Specifically, they are added at the midpoint of equally partiti    oned segments of the line.
+
+# Arguments
+
+* `probes::ProbeSystem`: the probe system whose `.position` field is to be updated
+* `x1::Vector{Float64}`: the first point defining the line along which probes are to be added
+* `x2::Vector{Float64}`: the second point defining the line along which probes are to be added
+* `n_probes::Int`: number of probes to be added
+* `i_last::Int`: index of the last probe in `probes`
+
+# Output
+
+* `i_last::Int`: updated index of the last probe in `probes`
+
+"""
+@inline function add_line!(probes::FastMultipole.ProbeSystem, x1, x2, n_probes, i_last)
+    dx = (x2 - x1) / n_probes
+    x = x1 + dx/2
+    for i in 1:n_probes
+        i_start += 1
+        probes.position[i_last + i] = x
+        x += dx
+    end
+    return i_last + n_probes
+end
+
 """
     reset!(probes)
 
@@ -122,3 +151,4 @@ function reset!(probes::ProbeSystem)
     reset!(probes.velocity)
     reset!(probes.velocity_gradient)
 end
+