The Evolution of the Skate
It is believed the first ice skates appeared around 400 AD. The skates below are the ulna and radius of a red deer. They may have been sledge-runners or they may have been bound on to the ankles to aid locomotion on ice. They were discovered in April 1869 in the site of the Gooch and Cousins' warehouse, London Wall. With them were two Roman sandal shoes.
Iron bladed skate used in the Netherlands around 1498
Below is the bladed skate of the 1770s. Note the forward morticed slot is very close to the toe. As the design of skates progressed this slot moved further back on the skate toward the ball of the foot.
The all-metal skate seems to have come into existence about 1800 simultaneously in Scotland, England and Germany. Henry Boswell, a resident of Oxford, England was the most enthusiastic and expert skater in Oxford and because of the difficulty he had skating outside edges, backwards and forward, single and double threes and even loops he and some fellow enthusiasts experimented with different lengths and curves of blades. The result was a skate without the projecting toe, with a heel slightly elongated and rounded and with a blade having a radius of seven feet. When the design was completed he had four dozen pairs made and supplied them to the Oxford skaters. With the new skate rapid progress was made and in 1838 a club was formed. The demand for Boswell's skates was so great a Sheffield firm took up their manufacture and they came into general use.
A photo of the Philadelphia Pattern can be seen at North American Skates- Manufactured
The following skate was highly recommended in 1874. It was quick and easy to put on. It has at its heel end a piece of metal shaped like a 't' instead of a screw which was to be let into the heel of a strong pair of boots. This hole in the boot was to be plugged when not used for skating with strong linen cloth so it didn't become too damaged to receive the 't' hook. In lieu of plugging, the valve shown could be used to cover up the hole and then thrown aside when the skate was to be fastened on. With this method no heel straps were necessary.
The first ice skates used in America were of German origin and consisted of iron or steel runners culminating in a beautiful twist of several windings in front of the toe and ending in a brass finial. The part of the runner that touched the ice had a gutter cut into it. It was fastened by several straps that were often stuck full of sticks to tighten them to an exruciating degree. This was the greatest objection to this design of skate and led to the creation of 'club' skates that clamped in various ways to the boot.
Recreational skaters in the early 1890's were recommended to use skates with a wooden footstock and leather fastenings. Apparently metal skates such as Club skates were seldom secure and made a disagreeable jar and clatter. It was recommended that the prow be no more than 2 inches above the surface of the ice. The curved prow allowed skaters to pass more easily over rough ice but too much curl made it difficult to scale steep snow banks and they were carried less easily in the handbag.
From about 1880 to 1905 there was very little change either in the design or the radius of the skate used in America. The figures skated were very small and the small radius of the skate made them possible. The Diamond Toe increased the vogue of toe movments and pirouettes. This style of skating, unknown anywhere else other than Canada, became known as 'barrel-head skating' from the suggestion that the skater's entire repertoire could be performed on the head of a barrel. This automatically barred North American skaters from World competition owing to the great difference of style and standards.
English figure skaters agreed that a skate blade for figure skating should be the true segment of a circle having a radius of seven feet- some accomplished skaters used a blade with a radius of six feet. The really good skater could skate on any of the blades in vogue at that time.

Formerly, everyone used acute angled edges. About 1875 the members of the London Skating Club had their skates ground to an obtuse angle but this lasted only a few weeks after which they came to the happy medium of right angled blades.

Acute angles were so sharp they set up great friction by cutting in too deeply. The obtuse angle blade when used by a heavy man on soft ice was delightful but if the ice was hard they were very slippery.

A skate with a curvature of nine feet radius distributed the weight bearing over a larger area but then turns and loops became difficult. The Swedes and Norwegians who practiced figure skating of an acrobatic nature had their skates ground to a five foot radius and increased the pivoting power by using convex sides.
                                                                Acute         Right Angle        Obtuse

In the early 1880's Captain Dowler, a member of the London Skating Club, took out a patent for a skate with concave sides. His idea was that when the skate was inclined the concave side would bring a greater portion of the blade in actual contact the ice increasing the bearing surface and diminishing friction. Figure skating on Dowler skates was less fatiguing than on right angled skates.     
    The skate below is from around 1913. It was screwed to the boots and had highly tempered fine steel on the bearing surface. The radius is five and a half to six feet. The edges are acutely angled and the width of the blade barely one quarter of an inch. The rounded prow fit tightly against the boot in which a slight notch was sometimes cut to receive it.    .
Sources
The Badminton Library. Heathcote, Tebutt & Witham
Skating. Douglas Adams                                                                                                                    
The Skaters Text Book. Frank Swift, Marvin Clark
The Art of Skating, International Style. E & M Syers
The Art of Skating. Irving Brokaw
A System of Figure Skating. H. E. Vandervell & T. Maxwell Witham
Wonderful World of Skates. Arthur Goodfellow
Ice Skating. Nigel Brown