William Blencowe's "Safest and Most Expeditious" Cipher

I uploaded a new article "William Blencowe's "Safest and Most Expeditious" Cipher". Blencowe was a grandson of the celebrated mathematician and codebreaker, John Wallis.
The example ciphertext consists of an interesting mix of single letters and bigrams:

a.c.e.o.t.ds,th.al,th.an,th,es,an,my,be,m.n.t.o.nd,jo.H.sh,y,in.y.
A.w.n,th,e.de.in.pi.sa.I.A.g.su.r.to,ye,ho.e,th.c.wth,de.re,en.t.at,
r.il,ti.A.n.nb.te.sts,nd,ri.rm.ot,re,d,n.m.m.r.ar,nd,ar,ty,us.i.m.c
in,a.e,d,h,ro.to,y.ig.&,of,to,ou,a.b.d.g.f.p,no,n.is,d,a.p,k.
ye,b.th.th.of,u.m.n.hl.th.t.S.t.n.e.ye,xt,u.w.A.ho,en.o.w.Ja.I
th,l.F.pe,n.e,h,hi.rs,ar,ty,la.ki.a.r.in,e.fo.to.m,w.tw.th.nd,ng,Sr,
no.le,at,ey,th.gh,ar.ed,an.e.w.co.h.n,h,a.n.e.E.ey,pa.ou.d,an,is,as.
r.p.m,g.f.c,a.n.do,ll,b.m,d.g.b.d.m,p.q.b,s.r,d.c,a.n

After all, however, this is essentially a columnar transposition cipher with some additional twists. Using bigrams may mislead the codebreaker at first, but once transposition is suspected, they would help codebreaking rather than prevent it.