The elaborate outfits worn by these two little sisters are typical of the styles of the 1860s. Bell-shaped crinolines were worn at a shorter length by girls and reveal lace-up boots with patent leather toecaps. Their hair is parted in the middle and the straw bonnet matches the monochrome theme of their summer clothes.
Thankfully someone had the foresight to date the image which was taken in 1862 by the studio of F.H. Mares, whose work I have previously featured on this blog. The studio was located on Grafton Street near to the business of Mademoiselle de Groots. According to The Irish Times of Wednesday 22nd October 1862, her warehouse at number 45 sold the following items which she had recently obtained in Paris: “corsets et ceintures; lingerie, crinolines, zouaves, etc.”
The Zouave jacket is a coloured and sometimes braided garment based on the uniform of an infantry regiment of the French Army. The were very popular during this period as illustrated by fashion plates from Godey’s Magazine.
Jacolette: 
I love these stylish children. Sad to imagine them in 20 years, with their waists nipped in, or in even 40 years, bent and pushed into that awful ‘S’ silhouette!
I love the collection you have here!