1882.] 



MICKOSCOPICAL JOUENAL 



23 



and smell. Underthemicroscope.it 

 also much resembles suene, but the 

 balls of crystals seem looser and more 

 free needle-shaped crystals are pre- 

 sent, there is more granular matter, 

 and there are seen fine fibres which 

 do not polarize, which are probably 

 fibres of connective tissue derived 

 from the fat, and salt-crystals are 

 present (fig. 7). 





^PO 



r.c 





Fig. 7. — Oleomargarine. 



There is another adulteration at- 

 tributed to the butter dealers, which 

 is the mixture of powdered soapstone, 

 to increase its weight. It has been 

 charged that about six pounds of fine- 

 ly powdered soapstone can be mixed 

 with fifty pounds of butter without its 

 presence being perceptible to the 

 taste — indeed, it is claimed that this 

 unpalatable soapstone powder (used 

 for foundry facings) has neither taste 

 nor smell, and cannot be detected by 

 the user — and direct experiment has 

 verified the assertion. With the mi- 

 croscope, however, such an adultera- 

 tion (being 12 per cent.) is readily 

 detected, as the soapstone powder is 

 coarser than the granular matter of 

 the butter, and by melting some of 

 the suspected butter in a test-tube 

 and examining the sediment, if soap- 

 stone is present it will at once be de- 

 tected. I have not found this adul- 

 teration myself, in butter sold by any 

 retailer, and if practised at all, it 

 is probably in butter packed for ship- 

 ment abroad. Truly, if butter can be 

 made half (and often two-thirds) of 

 lard and then 12 per cent, of soap- 

 stone added, without the ordinary 

 consumer being able to detect it, the 

 outlook for those who are particular 

 about their eating is not encouraging. 

 Will the skilled adulterator succeed 



when he tries his practised hand on 

 eggs? 



o 



Prof. Roger's Micrometers. 



BY J. D. COX, F. R. M. S. 



It is well known that Prof. William 

 A. Rogers, of Harvard Observatory, 

 has for some years been devoting much 

 time, labor and money to perfect- 

 ing our means for the accurate and 

 scientific comparison and subdivision 

 of standards of length. A machine 

 made for him at the Waltham Watch 

 Manufactory has been brought, under 

 his tireless efforts, to a degree of per- 

 fection which would seem to leave 

 very little to be desired. Results 

 which he has reached in the ruling of 

 micrometer plates, are so far superior 

 to what has been heretofore done, that 

 every one who has occasion for mi- 

 crometic work must be interested in 

 them, and the scientific world ought 

 not to be slow in proving and recog- 

 nizing the value of the improvement 

 made. 



I have a glass micrometer plate 

 ruled by him about a year ago, con- 

 taining subdivisions of the inch and 

 the centimetre in the following form: 

 I St. a band of five hundred lines -s^To 

 inch distant from each other. These- 

 are finely but rather strongly ruled. 

 2d. This band is continued across the 

 plate to the right by five hundred more 

 lines of the same spacing, but ruled 

 very lightly and delicately. 3d. Be- 

 neath band No. i, is another of the 

 sanie spacing ruled very lightly like 

 No. 2. 4th. This last is continued 

 across the plate by one ruled more 

 strongly, like No. i. 5th. Under No. 



3 is a band of five hundred lines, one- 

 thousandth of a centimetre apart, 

 strongly ruled, and this is followed by 

 a sixth, seventh and eight band in the 

 same relation to this that Nos. 2, 3 and 



4 are to No. i and with alternation of 

 the strong and light ruling. 



The whole plate is thus a sort of 

 checker-board of alternating parallelo- 

 grams strongly and lightly ruled, of 

 which the upper four are subdivisions 



