Snowshoe cat very vocal, though their voices are not as loud as the Siamese, a cat found in their breed heritage. They are noted as being very intelligent and have the ability to learn tricks and open doors. These cats also enjoy water, and may swim. In the 1960s, a cat, owned by Siamese cat breeder Dorothy Hinds-Daugherty, produced a litter of Siamese kittens in Philadelphia, Pennsylvania. Three of the kittens had unique markings, consisting of white points and feet. Intrigued by their looks, she began working to breed cats like them, using seal point Siamese with bicolor American Shorthairs. The offspring
Crystallographic point group known as a crystal class. There are infinitely many three-dimensional point groups. However, the crystallographic restriction of the infinite families of general point groups results in there being only 32 crystallographic point groups. These 32 point groups are one-and-the same as the 32 types of morphological (external) crystalline symmetries derived in 1830 by Johann Friedrich Christian Hessel from a consideration of observed crystal forms. The point group of a crystal, among other things, determines directional variation of the physical properties that arise from its structure, including optical properties such as whether it is birefringent, or whether it shows the Pockels